Pro 97 volume problems
I recently purchased a pro97 scanner in near new condition over the internet
through ebay. The item was listed as having very low audio such as one has to place the speaker next to his ear to hear the broadcast so I took a chance and bought it for 45 dollars. I got it in yesterday and it is totally new! packaging, all accessories, books and not a scratch on it. Well. I unpack it and install freshly charged (new) batteries and I go to playing with it..first..a weather channel..sure enough, very low volume even when cranked to the fullest it is still at the same volume level. I went ahead and took out the four back cover screws and examined the area where the volume pot is soldered and took some readings. center tap is about 2.1kohm and 200 k ohm on the non grounded side. (this is without power applied) in the area of the volume/squelch pot, are 3 tiny pots and 3 test points...(this is all from memory as the scanner is closed up now). I was hoping for a misplaced speaker magnet or something simpler and the circuits are ungodly miniature and even the audio amp chip is about the size of an op amp on most regular size circuits. The doggone thing is so new looking, that it may be swapped with a newer one from radio shack (by swapping backplates) but I don't dare attempt the dishonest. Anyway, any suggestions to resolve my dillemma...could it be possible that I have a defective volume pot? No amount of regulation seems to affect the audio at all. The channel beep come through loud and clear but it seems that either the preamp from the radio is set too low or the pot is defective/soldered wrong. Of course, the possibility of a bad IC has crossed my mind as well. Any suggestions? No warranty so all I have is either a repairman or my good wits and some knowledge to help correct the problem. Btw, the sqelch seems to work OK. Your input would be greally appreciated, Allen |
Pro 97 volume problems
Might be a bad pot. If you have a meter, with power off measure resistance
from center terminal of the pot to ground. Turn the volume knob through its range. If there is no resistance change, order a new pot. This is what I have for ordering the volume pot: 12429163 POT VOLUME 50K OHM $15.89. Be sure to verify the correct part number if you do order one so you don't get the wrong part. "Allen Crawford" wrote in message ... I recently purchased a pro97 scanner in near new condition over the internet through ebay. The item was listed as having very low audio such as one has to place the speaker next to his ear to hear the broadcast so I took a chance and bought it for 45 dollars. I got it in yesterday and it is totally new! packaging, all accessories, books and not a scratch on it. Well. I unpack it and install freshly charged (new) batteries and I go to playing with it..first..a weather channel..sure enough, very low volume even when cranked to the fullest it is still at the same volume level. I went ahead and took out the four back cover screws and examined the area where the volume pot is soldered and took some readings. center tap is about 2.1kohm and 200 k ohm on the non grounded side. (this is without power applied) in the area of the volume/squelch pot, are 3 tiny pots and 3 test points...(this is all from memory as the scanner is closed up now). I was hoping for a misplaced speaker magnet or something simpler and the circuits are ungodly miniature and even the audio amp chip is about the size of an op amp on most regular size circuits. The doggone thing is so new looking, that it may be swapped with a newer one from radio shack (by swapping backplates) but I don't dare attempt the dishonest. Anyway, any suggestions to resolve my dillemma...could it be possible that I have a defective volume pot? No amount of regulation seems to affect the audio at all. The channel beep come through loud and clear but it seems that either the preamp from the radio is set too low or the pot is defective/soldered wrong. Of course, the possibility of a bad IC has crossed my mind as well. Any suggestions? No warranty so all I have is either a repairman or my good wits and some knowledge to help correct the problem. Btw, the sqelch seems to work OK. Your input would be greally appreciated, Allen |
Pro 97 volume problems
what does it do to a set of phones or ext speaker?
my thought lie with a naff speaker. even though the beep is ok. have you a sig gen? or maybe stick a radio from the eaphone socket to two bear wire and put them across the scanners speaker after disconnecting the scanners own feed, does it work ok then? you need to find out if it is the scanner at fault or the speaker as the dirst step. if an external audio source works, then time to scope the i/p & o/pof the audio chip. should be easy to do. mike "Allen Crawford" wrote in message ... I recently purchased a pro97 scanner in near new condition over the internet through ebay. The item was listed as having very low audio such as one has to place the speaker next to his ear to hear the broadcast so I took a chance and bought it for 45 dollars. I got it in yesterday and it is totally new! packaging, all accessories, books and not a scratch on it. Well. I unpack it and install freshly charged (new) batteries and I go to playing with it..first..a weather channel..sure enough, very low volume even when cranked to the fullest it is still at the same volume level. I went ahead and took out the four back cover screws and examined the area where the volume pot is soldered and took some readings. center tap is about 2.1kohm and 200 k ohm on the non grounded side. (this is without power applied) in the area of the volume/squelch pot, are 3 tiny pots and 3 test points...(this is all from memory as the scanner is closed up now). I was hoping for a misplaced speaker magnet or something simpler and the circuits are ungodly miniature and even the audio amp chip is about the size of an op amp on most regular size circuits. The doggone thing is so new looking, that it may be swapped with a newer one from radio shack (by swapping backplates) but I don't dare attempt the dishonest. Anyway, any suggestions to resolve my dillemma...could it be possible that I have a defective volume pot? No amount of regulation seems to affect the audio at all. The channel beep come through loud and clear but it seems that either the preamp from the radio is set too low or the pot is defective/soldered wrong. Of course, the possibility of a bad IC has crossed my mind as well. Any suggestions? No warranty so all I have is either a repairman or my good wits and some knowledge to help correct the problem. Btw, the sqelch seems to work OK. Your input would be greally appreciated, Allen |
Pro 97 volume problems
Thanks frank,
is this for the vol/squelch combi or can they be seperated? regards, Allen "Frank346" wrote in message ... Might be a bad pot. If you have a meter, with power off measure resistance from center terminal of the pot to ground. Turn the volume knob through its range. If there is no resistance change, order a new pot. This is what I have for ordering the volume pot: 12429163 POT VOLUME 50K OHM $15.89. Be sure to verify the correct part number if you do order one so you don't get the wrong part. "Allen Crawford" wrote in message ... I recently purchased a pro97 scanner in near new condition over the internet through ebay. The item was listed as having very low audio such as one has to place the speaker next to his ear to hear the broadcast so I took a chance and bought it for 45 dollars. I got it in yesterday and it is totally new! packaging, all accessories, books and not a scratch on it. Well. I unpack it and install freshly charged (new) batteries and I go to playing with it..first..a weather channel..sure enough, very low volume even when cranked to the fullest it is still at the same volume level. I went ahead and took out the four back cover screws and examined the area where the volume pot is soldered and took some readings. center tap is about 2.1kohm and 200 k ohm on the non grounded side. (this is without power applied) in the area of the volume/squelch pot, are 3 tiny pots and 3 test points...(this is all from memory as the scanner is closed up now). I was hoping for a misplaced speaker magnet or something simpler and the circuits are ungodly miniature and even the audio amp chip is about the size of an op amp on most regular size circuits. The doggone thing is so new looking, that it may be swapped with a newer one from radio shack (by swapping backplates) but I don't dare attempt the dishonest. Anyway, any suggestions to resolve my dillemma...could it be possible that I have a defective volume pot? No amount of regulation seems to affect the audio at all. The channel beep come through loud and clear but it seems that either the preamp from the radio is set too low or the pot is defective/soldered wrong. Of course, the possibility of a bad IC has crossed my mind as well. Any suggestions? No warranty so all I have is either a repairman or my good wits and some knowledge to help correct the problem. Btw, the sqelch seems to work OK. Your input would be greally appreciated, Allen |
Pro 97 volume problems
"mikeFNB" wrote in message ... what does it do to a set of phones or ext speaker? my thought lie with a naff speaker. even though the beep is ok. have you a sig gen? or maybe stick a radio from the eaphone socket to two bear wire and put them across the scanners speaker after disconnecting the scanners own feed, does it work ok then? you need to find out if it is the scanner at fault or the speaker as the dirst step. if an external audio source works, then time to scope the i/p & o/pof the audio chip. should be easy to do. mike Thanks Mike, I tried an amplified source via the earphone. The Amplifier was a Klipsch 2.1 (200 watts) the audio was barely intelligible. the background hiss was overbearing and a beep tone at the same amplified volume level was well beyond tolerability. I will try your other suggestions as I do have a tone generator that I could get out of mothballs. regards, Allen |
Pro 97 volume problems
Allen Crawford wrote:
I recently purchased a pro97 scanner in near new condition over the internet through ebay. The item was listed as having very low audio such as one has to place the speaker next to his ear to hear the broadcast so I took a chance and bought it for 45 dollars. I got it in yesterday and it is totally new! packaging, all accessories, books and not a scratch on it. Well. I unpack it and install freshly charged (new) batteries and I go to playing with it..first..a weather channel..sure enough, very low volume even when cranked to the fullest it is still at the same volume level. I went ahead and took out the four back cover screws and examined the area where the volume pot is soldered and took some readings. center tap is about 2.1kohm and 200 k ohm on the non grounded side. (this is without power applied) in the area of the volume/squelch pot, are 3 tiny pots and 3 test points...(this is all from memory as the scanner is closed up now). I was hoping for a misplaced speaker magnet or something simpler and the circuits are ungodly miniature and even the audio amp chip is about the size of an op amp on most regular size circuits. The doggone thing is so new looking, that it may be swapped with a newer one from radio shack (by swapping backplates) but I don't dare attempt the dishonest. Anyway, any suggestions to resolve my dillemma...could it be possible that I have a defective volume pot? No amount of regulation seems to affect the audio at all. The channel beep come through loud and clear but it seems that either the preamp from the radio is set too low or the pot is defective/soldered wrong. Of course, the possibility of a bad IC has crossed my mind as well. Any suggestions? No warranty so all I have is either a repairman or my good wits and some knowledge to help correct the problem. Btw, the sqelch seems to work OK. Your input would be greally appreciated, Allen Is the beep affected by the volume pot? I have the Pro-96 and the volume control is awfully hair-trigger - goes from nothing to too damn loud in the first few degrees of movement and then there's not much left for the rest of the adjustment. It may be a 'design feature', though yours suggests an actual fault of some sort. Can you get to the volume pot and listen with an earpiece on the various pins to ground? Cheers. Ken |
Pro 97 volume problems
I believe it is for the combination. That might account for the high price.
The beep probably bypasses the volume control in the circuit. Since it is loud and clear, the audio amp chip is ok and the speaker is too. Note that the volume pot is 50K from one end terminal to the other. If you get a higher reading than that from the center terminal to either end, that is a clue that the pot is probably bad. "Allen Crawford" wrote in message ... Thanks frank, is this for the vol/squelch combi or can they be seperated? regards, Allen "Frank346" wrote in message ... Might be a bad pot. If you have a meter, with power off measure resistance from center terminal of the pot to ground. Turn the volume knob through its range. If there is no resistance change, order a new pot. This is what I have for ordering the volume pot: 12429163 POT VOLUME 50K OHM $15.89. Be sure to verify the correct part number if you do order one so you don't get the wrong part. "Allen Crawford" wrote in message ... I recently purchased a pro97 scanner in near new condition over the internet through ebay. The item was listed as having very low audio such as one has to place the speaker next to his ear to hear the broadcast so I took a chance and bought it for 45 dollars. I got it in yesterday and it is totally new! packaging, all accessories, books and not a scratch on it. Well. I unpack it and install freshly charged (new) batteries and I go to playing with it..first..a weather channel..sure enough, very low volume even when cranked to the fullest it is still at the same volume level. I went ahead and took out the four back cover screws and examined the area where the volume pot is soldered and took some readings. center tap is about 2.1kohm and 200 k ohm on the non grounded side. (this is without power applied) in the area of the volume/squelch pot, are 3 tiny pots and 3 test points...(this is all from memory as the scanner is closed up now). I was hoping for a misplaced speaker magnet or something simpler and the circuits are ungodly miniature and even the audio amp chip is about the size of an op amp on most regular size circuits. The doggone thing is so new looking, that it may be swapped with a newer one from radio shack (by swapping backplates) but I don't dare attempt the dishonest. Anyway, any suggestions to resolve my dillemma...could it be possible that I have a defective volume pot? No amount of regulation seems to affect the audio at all. The channel beep come through loud and clear but it seems that either the preamp from the radio is set too low or the pot is defective/soldered wrong. Of course, the possibility of a bad IC has crossed my mind as well. Any suggestions? No warranty so all I have is either a repairman or my good wits and some knowledge to help correct the problem. Btw, the sqelch seems to work OK. Your input would be greally appreciated, Allen |
Pro 97 volume problems
Component failure may have cause the IF freq. to shift off of the correct
freq. HJ |
Pro 97 volume problems
"Ken Taylor" wrote in message ... Allen Crawford wrote: I recently purchased a pro97 scanner in near new condition over the internet through ebay. The item was listed as having very low audio such as one has to place the speaker next to his ear to hear the broadcast so I took a chance and bought it for 45 dollars. I got it in yesterday and it is totally new! packaging, all accessories, books and not a scratch on it. Well. I unpack it and install freshly charged (new) batteries and I go to playing with it..first..a weather channel..sure enough, very low volume even when cranked to the fullest it is still at the same volume level. I went ahead and took out the four back cover screws and examined the area where the volume pot is soldered and took some readings. center tap is about 2.1kohm and 200 k ohm on the non grounded side. (this is without power applied) in the area of the volume/squelch pot, are 3 tiny pots and 3 test points...(this is all from memory as the scanner is closed up now). I was hoping for a misplaced speaker magnet or something simpler and the circuits are ungodly miniature and even the audio amp chip is about the size of an op amp on most regular size circuits. The doggone thing is so new looking, that it may be swapped with a newer one from radio shack (by swapping backplates) but I don't dare attempt the dishonest. Anyway, any suggestions to resolve my dillemma...could it be possible that I have a defective volume pot? No amount of regulation seems to affect the audio at all. The channel beep come through loud and clear but it seems that either the preamp from the radio is set too low or the pot is defective/soldered wrong. Of course, the possibility of a bad IC has crossed my mind as well. Any suggestions? No warranty so all I have is either a repairman or my good wits and some knowledge to help correct the problem. Btw, the sqelch seems to work OK. Your input would be greally appreciated, Allen Is the beep affected by the volume pot? I have the Pro-96 and the volume control is awfully hair-trigger - goes from nothing to too damn loud in the first few degrees of movement and then there's not much left for the rest of the adjustment. It may be a 'design feature', though yours suggests an actual fault of some sort. Can you get to the volume pot and listen with an earpiece on the various pins to ground? Cheers. Ken Ken, the "beeptone" is virtually unaffected by the volume control and remains constant from the near off position to max volume. I only wish I could get to the contacts while the unit is powered up but it is sandwiched with a lower speaker/display/keypad board and they will not operate when separated. so all my experimentation must be done with the component side only:-(\ regards, Allen |
Pro 97 volume problems
"Frank346" wrote in message ... I believe it is for the combination. That might account for the high price. The beep probably bypasses the volume control in the circuit. Since it is loud and clear, the audio amp chip is ok and the speaker is too. Note that the volume pot is 50K from one end terminal to the other. If you get a higher reading than that from the center terminal to either end, that is a clue that the pot is probably bad. Frank, I am inclined to go with that too. I am going to have to get the spouse to help with the pot turning while I hold the fluke leads. I will give back the readings with respect to ground later and see what you think. there is a stack of 3 soldered leads which leads me to believe that 3 are on/off, 3 are volume, and 3 are squelch...darn squelch definately wants to parallel the movement of the volume too....damn poor design for such a nice spec'd receiver. regards, Allen |
Pro 97 volume problems
"Honest John" wrote in message ... Component failure may have cause the IF freq. to shift off of the correct freq. HJ Thanks Honest John, Well, the scanner is still displaying, responding to calls, and giving low audible output. But if your theory is correct, I'm screwed:-(...I won't give up hope...I am going to try the pot and hope like heck that is all it is. I would fare better off buying a new one if I had the problem you described. Thanks for the input and let's hope for non-failure of component/s:-) regards, Allen |
Pro 97 volume problems
On Wed, 01 Mar 2006 02:28:26 GMT, "Allen Crawford"
wrote: I would fare better off buying a new one Try hanging a 47k resistor between the high end and the center pin of the pot and keep the pot about at the center. It's not a fix, but if it works a little, you know the pot is shot (open on the high end). You wouldn't be happy spending $15 for a pot to discover that it's not the pot that's the problem. |
Pro 97 volume problems
Just wondering, if you tried to do a re-set of the radio? I doubt that
would do anything, but it might not hurt. -SMTP "Allen Crawford" wrote in message ... I recently purchased a pro97 scanner in near new condition over the internet through ebay. The item was listed as having very low audio such as one has to place the speaker next to his ear to hear the broadcast so I took a chance and bought it for 45 dollars. I got it in yesterday and it is totally new! packaging, all accessories, books and not a scratch on it. Well. I unpack it and install freshly charged (new) batteries and I go to playing with it..first..a weather channel..sure enough, very low volume even when cranked to the fullest it is still at the same volume level. I went ahead and took out the four back cover screws and examined the area where the volume pot is soldered and took some readings. center tap is about 2.1kohm and 200 k ohm on the non grounded side. (this is without power applied) in the area of the volume/squelch pot, are 3 tiny pots and 3 test points...(this is all from memory as the scanner is closed up now). I was hoping for a misplaced speaker magnet or something simpler and the circuits are ungodly miniature and even the audio amp chip is about the size of an op amp on most regular size circuits. The doggone thing is so new looking, that it may be swapped with a newer one from radio shack (by swapping backplates) but I don't dare attempt the dishonest. Anyway, any suggestions to resolve my dillemma...could it be possible that I have a defective volume pot? No amount of regulation seems to affect the audio at all. The channel beep come through loud and clear but it seems that either the preamp from the radio is set too low or the pot is defective/soldered wrong. Of course, the possibility of a bad IC has crossed my mind as well. Any suggestions? No warranty so all I have is either a repairman or my good wits and some knowledge to help correct the problem. Btw, the sqelch seems to work OK. Your input would be greally appreciated, Allen |
Pro 97 volume problems
"Mr. Man with the Master Plan" wrote in message ... Just wondering, if you tried to do a re-set of the radio? I doubt that would do anything, but it might not hurt. -SMTP Well shoot fire, I am receptive to anything right about now...I figure that the worst it could do is delate all the pre-sets...but what the hay...I'll give it a whirl! Gonna have to consult the manual to find it's where-abouts! Cheers!, Allen "Allen Crawford" wrote in message ... I recently purchased a pro97 scanner in near new condition over the internet through ebay. The item was listed as having very low audio such as one has to place the speaker next to his ear to hear the broadcast so I took a chance and bought it for 45 dollars. I got it in yesterday and it is totally new! packaging, all accessories, books and not a scratch on it. Well. I unpack it and install freshly charged (new) batteries and I go to playing with it..first..a weather channel..sure enough, very low volume even when cranked to the fullest it is still at the same volume level. I went ahead and took out the four back cover screws and examined the area where the volume pot is soldered and took some readings. center tap is about 2.1kohm and 200 k ohm on the non grounded side. (this is without power applied) in the area of the volume/squelch pot, are 3 tiny pots and 3 test points...(this is all from memory as the scanner is closed up now). I was hoping for a misplaced speaker magnet or something simpler and the circuits are ungodly miniature and even the audio amp chip is about the size of an op amp on most regular size circuits. The doggone thing is so new looking, that it may be swapped with a newer one from radio shack (by swapping backplates) but I don't dare attempt the dishonest. Anyway, any suggestions to resolve my dillemma...could it be possible that I have a defective volume pot? No amount of regulation seems to affect the audio at all. The channel beep come through loud and clear but it seems that either the preamp from the radio is set too low or the pot is defective/soldered wrong. Of course, the possibility of a bad IC has crossed my mind as well. Any suggestions? No warranty so all I have is either a repairman or my good wits and some knowledge to help correct the problem. Btw, the sqelch seems to work OK. Your input would be greally appreciated, Allen |
Pro 97 volume problems
"Allen Crawford" wrote in message ... "Mr. Man with the Master Plan" wrote in message ... Just wondering, if you tried to do a re-set of the radio? I doubt that would do anything, but it might not hurt. -SMTP Well shoot fire, I am receptive to anything right about now...I figure that the worst it could do is delate all the pre-sets...but what the hay...I'll give it a whirl! Gonna have to consult the manual to find it's where-abouts! Cheers!, Allen "Allen Crawford" wrote in message ... I recently purchased a pro97 scanner in near new condition over the internet through ebay. The item was listed as having very low audio such as one has to place the speaker next to his ear to hear the broadcast so I took a chance and bought it for 45 dollars. I got it in yesterday and it is totally new! packaging, all accessories, books and not a scratch on it. Well. I unpack it and install freshly charged (new) batteries and I go to playing with it..first..a weather channel..sure enough, very low volume even when cranked to the fullest it is still at the same volume level. I went ahead and took out the four back cover screws and examined the area where the volume pot is soldered and took some readings. center tap is about 2.1kohm and 200 k ohm on the non grounded side. (this is without power applied) in the area of the volume/squelch pot, are 3 tiny pots and 3 test points...(this is all from memory as the scanner is closed up now). I was hoping for a misplaced speaker magnet or something simpler and the circuits are ungodly miniature and even the audio amp chip is about the size of an op amp on most regular size circuits. The doggone thing is so new looking, that it may be swapped with a newer one from radio shack (by swapping backplates) but I don't dare attempt the dishonest. Anyway, any suggestions to resolve my dillemma...could it be possible that I have a defective volume pot? No amount of regulation seems to affect the audio at all. The channel beep come through loud and clear but it seems that either the preamp from the radio is set too low or the pot is defective/soldered wrong. Of course, the possibility of a bad IC has crossed my mind as well. Any suggestions? No warranty so all I have is either a repairman or my good wits and some knowledge to help correct the problem. Btw, the sqelch seems to work OK. Your input would be greally appreciated, Allen OK..there is not hard reset button on this one, like older models. You initialize by going through a sequence of turning off/then on the scanner. While the splash screen reads multi system trunking...etc. (you usually have 5 secs) then you press 0 1 enter and wait about 5 seconds as it tells you that it is initializing. You lose all your presets but mine was set by RS anyway. No help though...still just as quiet as before...He! he! sorta reminds me of the day when I got my first crystal set:-) Thanks all for the suggestions, regards to all, Allen |
Pro 97 volume problems
On Tue, 28 Feb 2006 23:56:58 GMT, "Allen Crawford"
wrote: I recently purchased a pro97 scanner in near new condition over the internet through ebay. The item was listed as having very low audio such as one has to place the speaker next to his ear to hear the broadcast so I took a chance and bought it for 45 dollars. I got it in yesterday and it is totally new! packaging, all accessories, books and not a scratch on it. Well. I unpack it and install freshly charged (new) batteries and I go to playing with it..first..a weather channel..sure enough, very low volume even when cranked to the fullest it is still at the same volume level. I went ahead and took out the four back cover screws and examined the area where the volume pot is soldered and took some readings. center tap is about 2.1kohm and 200 k ohm on the non grounded side. (this is without power applied) in the area of the volume/squelch pot, are 3 tiny pots and 3 test points...(this is all from memory as the scanner is closed up now). I was hoping for a misplaced speaker magnet or something simpler and the circuits are ungodly miniature and even the audio amp chip is about the size of an op amp on most regular size circuits. The doggone thing is so new looking, that it may be swapped with a newer one from radio shack (by swapping backplates) but I don't dare attempt the dishonest. Anyway, any suggestions to resolve my dillemma...could it be possible that I have a defective volume pot? No amount of regulation seems to affect the audio at all. The channel beep come through loud and clear but it seems that either the preamp from the radio is set too low or the pot is defective/soldered wrong. Of course, the possibility of a bad IC has crossed my mind as well. Any suggestions? No warranty so all I have is either a repairman or my good wits and some knowledge to help correct the problem. Btw, the sqelch seems to work OK. Your input would be greally appreciated, Allen Allen, I had a PRO-96 that had the *exact* same problem... I'm not sure how similar it is to the PRO-97, so the following may or may not be of any use... but might be worth a try, or may give you some ideas... Have a look at the picture at: http://www.ninemoons.com/~daf/images/PRO-96.jpg After trying all the obvious stuff, I found that very gently pushing down on the edge of the circuit board (with a non-metallic object :-) in the area outlined in red that the volome would increase tremendously. It was quite touchy, and seemed to be fairly localized to that general area. Volume would always return to it's previously "barely audible" state when pressure was released. I suspected a micro-crack in a solder joint or possibly one of the "plated-through" holes. A "cold" solder joint was another possibility... I removed the board and inspected both sides very carefully in that area with the highest power magnifier I had on hand (an eyepiece from a microscope...:-) Visual inspection didn't reveal anything, so I put the board back in and tried it again with the exact same results. This went on about 4 times until I finally got disgusted and drug out my trusty soldering iron! Having done a lot of bench work, I have a soldering iron with a tip about the size of a ball-point pin. I wouldn't recommend doing this with anything bigger, as it is very easy to overheat these SMT components. Using some high power reading glasses, I very briefly heated each of the solder joints "to melting" in the general area outlined in red, using no extra solder. (Very easy to use too much on these tiny pads!) I did add very minute amounts of solder to some of the plated-through holes until I could tell from both sides they were "soldered-through" After putting things back together - VOILA! Normal sound levels! The final test was when I could get no changes in the (now normal) volume by pushing down in area that had been so touchy before. Hope this helps... -Dan ------ Disclaimer! I'm NOT responsible if you muck things up worse!! |
Pro 97 volume problems
"Dan" wrote in message ... On Tue, 28 Feb 2006 23:56:58 GMT, "Allen Crawford" wrote: I recently purchased a pro97 scanner in near new condition over the internet through ebay. The item was listed as having very low audio such as one has to place the speaker next to his ear to hear the broadcast so I took a chance and bought it for 45 dollars. I got it in yesterday and it is totally new! packaging, all accessories, books and not a scratch on it. Well. I unpack it and install freshly charged (new) batteries and I go to playing with it..first..a weather channel..sure enough, very low volume even when cranked to the fullest it is still at the same volume level. I went ahead and took out the four back cover screws and examined the area where the volume pot is soldered and took some readings. center tap is about 2.1kohm and 200 k ohm on the non grounded side. (this is without power applied) in the area of the volume/squelch pot, are 3 tiny pots and 3 test points...(this is all from memory as the scanner is closed up now). I was hoping for a misplaced speaker magnet or something simpler and the circuits are ungodly miniature and even the audio amp chip is about the size of an op amp on most regular size circuits. The doggone thing is so new looking, that it may be swapped with a newer one from radio shack (by swapping backplates) but I don't dare attempt the dishonest. Anyway, any suggestions to resolve my dillemma...could it be possible that I have a defective volume pot? No amount of regulation seems to affect the audio at all. The channel beep come through loud and clear but it seems that either the preamp from the radio is set too low or the pot is defective/soldered wrong. Of course, the possibility of a bad IC has crossed my mind as well. Any suggestions? No warranty so all I have is either a repairman or my good wits and some knowledge to help correct the problem. Btw, the sqelch seems to work OK. Your input would be greally appreciated, Allen Allen, I had a PRO-96 that had the *exact* same problem... I'm not sure how similar it is to the PRO-97, so the following may or may not be of any use... but might be worth a try, or may give you some ideas... Have a look at the picture at: http://www.ninemoons.com/~daf/images/PRO-96.jpg After trying all the obvious stuff, I found that very gently pushing down on the edge of the circuit board (with a non-metallic object :-) in the area outlined in red that the volome would increase tremendously. It was quite touchy, and seemed to be fairly localized to that general area. Volume would always return to it's previously "barely audible" state when pressure was released. I suspected a micro-crack in a solder joint or possibly one of the "plated-through" holes. A "cold" solder joint was another possibility... I removed the board and inspected both sides very carefully in that area with the highest power magnifier I had on hand (an eyepiece from a microscope...:-) Visual inspection didn't reveal anything, so I put the board back in and tried it again with the exact same results. This went on about 4 times until I finally got disgusted and drug out my trusty soldering iron! Having done a lot of bench work, I have a soldering iron with a tip about the size of a ball-point pin. I wouldn't recommend doing this with anything bigger, as it is very easy to overheat these SMT components. Using some high power reading glasses, I very briefly heated each of the solder joints "to melting" in the general area outlined in red, using no extra solder. (Very easy to use too much on these tiny pads!) I did add very minute amounts of solder to some of the plated-through holes until I could tell from both sides they were "soldered-through" After putting things back together - VOILA! Normal sound levels! The final test was when I could get no changes in the (now normal) volume by pushing down in area that had been so touchy before. Hope this helps... -Dan ------ Disclaimer! I'm NOT responsible if you muck things up worse!! Thanks Dan, I have since got a pro2051 with missing speaker and ribbon cables and which I since managed to revive. My wife has since kidnapped the 2051 and this gives me some incentive to return to the PRO 97 project. Thanks for the tidbit of NFO and I will report back if things get better. FYI...I have already changed out 2 caps with the same capacitance but with a slightly higher volt rating. I was about to vye for a replacement pot. (squelch/vol) Your solution does sound compelling...I'll investigate. Thanks again and regards, Allen |
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