ray ) writes:
I got a FM broadcast band radio from the dollar store. In it it has a
16 pin SMD IC of unknown brand. Although I plan using these for my
10Ghz gunnplexers. There is one coil and a varactor diode. They use
push button up tuning and another to reset to the low end of the band.
I don't find any parts for an IF so it must be a TRF style receiver.
It has a stereo headphone jack but it's not stereo, and the headphone
cable is used for the antenna, And it runs off of 3 VDC. I'd like to
know what this chip is so I can take it down to 30Mhz.
Later,
Ray KC8OJU
I bought one of those two button radios, and below is a post I
wrote in response to a similar question shortly after I opened
the thing up back in March.
Michael VE2BVW
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Gary Tait ) writes:
I am looking for the datasheet for the chip in one of those two button
radios
(you know,
scan, reset).
It says on it:
HWCAT 1036AH (datecode?)
CSC1033M
Ir is in a 16 pin SM DIP package.
I bought one of those recently, when they were on sale for $1.99 at
Pharmaprix (which is Shopper's Drug Mart in the rest of Canada).
I was simply curious about what was inside, and the price became
low enough that I didn't mind spending the money.
I had problems reading the IC at first. So I started out tracing
the circuit. At first, I thought/hoped it was the TDA7000, but
the pin count was wrong. I looked up that IC at the Phillips'
site (it was easier than trying to find where I'd stashed the
paper datasheet), and they made mention of similar ICs, including
two that had that tuning scheme. I went through them, and
the match was the TDA7088. Looking more carefully at the IC,
the "7088" was now visible, though it looked like it was a knockoff
or a cheap second source, rather than an IC that came from Phillips.
I'd say this is the same IC, since your "1033" could be a misread
of "7088".
Check the datasheet at
http://www.semiconductors.philips.com/pip/TDA7088.html
Likely by comparing the pinout from it with the actual circuit, you
will find a match.
I was going to post something about my findings, because they are a curiosity.
But I'm not sure where my notes are, or even where I put the circuit board.
The IC uses the same scheme as the TDA7000, ie a conversion to an IF
of about 70KHz, where an active filter can be used for selectivity.
And one of those Frequency Lock Loops which reduces the apparent deviation.
Then they throw in the circuitry for the tuning scheme.
Having once seen someone suggest using the TDA7000 as a direct conversion
receiver (when they were readily available at Radio Shack), they claimed
the mixer was double balanced, I couldn't help but think maybe these
radios would be a cheap local source for a mixer. Leave the IC on
the board, and just strip the unneeded parts of, wiring to the board
rather than wiring to that smd IC. I assume the big problem would
be that since the 7088 can't handle more than about 3V on the supply
line, it will be even worse for signal handling than the NE602 is said
to be. (And I am simply assuming it's a double balanced mixer.) But
for a couple of dollars, there are times when someone might need
a mixer that these radios can supply cheap and locally.
Michael