Drake R7 repair
 

I have one of these units in for repair. The person that I am repairing it
for is either too cheap to pay somebody for the schematic or too lazy to
follow up...............anyway, what I need is a scan of the schematic of
the power supply board. This is the later iteration that uses the TDA2002
audio amp chip as the oscillator vs the multivibrator circuit that is used
in the older iteration of the power supply. This fellow keeps sending me
scans of small sections of the power supply. He is getting these small scans
from somebody on the Drake mailing list. The person on the list is telling
him that the schematic is too large to scan. I will be glad to pay somebody
if they would be able to copy/reduct the size of the schematic so that it
can be scanned on a flatbed scanner.
If anybody can help me, I will be glad to pay you for a scan, and I will
then charge the owner of the receiver in turn. The problem is that the +24V
rail for the VCO tuning voltage is missing.
Thanks!

Pete

Drake R7 repair
 

Pete KE9OA wrote:

I have one of these units in for repair. The person that I am repairing it
for is either too cheap to pay somebody for the schematic or too lazy to
follow up...............anyway, what I need is a scan of the schematic of
the power supply board. This is the later iteration that uses the TDA2002
audio amp chip as the oscillator vs the multivibrator circuit that is used
in the older iteration of the power supply. This fellow keeps sending me
scans of small sections of the power supply. He is getting these small scans
from somebody on the Drake mailing list. The person on the list is telling
him that the schematic is too large to scan. I will be glad to pay somebody
if they would be able to copy/reduct the size of the schematic so that it
can be scanned on a flatbed scanner.
If anybody can help me, I will be glad to pay you for a scan, and I will
then charge the owner of the receiver in turn. The problem is that the +24V
rail for the VCO tuning voltage is missing.

After it's all fixed, I'd recommend that the individual run it off of a separate
12 volt supply. Might save some headaches down the road.

dxAce
Michigan
USA

Drake R7, R8, R8A and R8B
70' and 200' wires.

And as always, don't do business with the Huntington Investment Company.
Especially a fellow named Joseph Klein.

Drake R7 repair
 

I think you are right. The only receiver that I ever had that runs hotter
than the R7 is my old HF-2050. Now, that was hot!
I do have an R7 myself that I upgraded with better performance mixer,
replaced the displays, etc.
I keep it as a museum piece, along with my other Drake equipment.

Pete

"dxAce" wrote in message
...


Pete KE9OA wrote:

I have one of these units in for repair. The person that I am repairing
it
for is either too cheap to pay somebody for the schematic or too lazy to
follow up...............anyway, what I need is a scan of the schematic of
the power supply board. This is the later iteration that uses the TDA2002
audio amp chip as the oscillator vs the multivibrator circuit that is
used
in the older iteration of the power supply. This fellow keeps sending me
scans of small sections of the power supply. He is getting these small
scans
from somebody on the Drake mailing list. The person on the list is
telling
him that the schematic is too large to scan. I will be glad to pay
somebody
if they would be able to copy/reduct the size of the schematic so that it
can be scanned on a flatbed scanner.
If anybody can help me, I will be glad to pay you for a scan, and I will
then charge the owner of the receiver in turn. The problem is that the
+24V
rail for the VCO tuning voltage is missing.

After it's all fixed, I'd recommend that the individual run it off of a
separate
12 volt supply. Might save some headaches down the road.

dxAce
Michigan
USA

Drake R7, R8, R8A and R8B
70' and 200' wires.

And as always, don't do business with the Huntington Investment Company.
Especially a fellow named Joseph Klein.

Drake R7 repair
 

I love that R7............that's while I still have mine. I did repair the
power supply on my friend's unit. The 24 volt supply has two iterations. The
early version uses a pair of TIP31s in a multivibrator configuration, is
rectified by a quad of 1N4148s, and regulated by a 78L24 regulator.
Later versions used what appears to be some kind of sine wave oscillator
that uses a TDA2002 audio amp chip. Everything else is the same, except an
LM317Z regulator is used for the 24 volt regulator.
The problem with the power supply on this unit was two bad electrolytic
coupling caps in the TDA2002 circuit. One of them is a 22uF unit whild the
other one is a 10uF unit. Replacing both of the caps solved the problem.
This is still one more problem with the unit.............the high band VCO
doesn't lock unless you are in the 28MHz range. This tells me that the
connection from the phase detector to the VCO is ok, as evidenced by the
tuning voltage being stuck high.
This also tells me that there is a break in the feedback loop between the
VCO output and the 1/N chain that feeds the input of the phase detector. I
will dig into that later...........................

Pete

"Me" wrote in message
...
On Sat, 1 Mar 2008 07:47:42 -0600, "Pete KE9OA"
wrote:

I think you are right. The only receiver that I ever had that runs hotter
than the R7 is my old HF-2050. Now, that was hot!
I do have an R7 myself that I upgraded with better performance mixer,
replaced the displays, etc.
I keep it as a museum piece, along with my other Drake equipment.

Pete


IMO, a properly working R7A still beats everything this side of a
Ten-Tec RX340.


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