Before i check voltages i have a question if you dont mind, on the P200 board only Q201 and Q204 read voltages both ways on diode test unit off, all others only show voltage drop one way, Is 201 and 204 different?
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2385 reconnect PS00 to P400 pin question
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Got it, thanks. I copied your measurements onto the schematic and most look close except Q209, Q210. (see schematic below)
The schematic voltages shown in ( ) are when an FM stereo station is tuned-in.
We need to figure out the function of Q209 & Q210 to see if that is a problem.
Hw do we find out the function of Q209 and Q210?
See attached, all good but number 8
Attachments
Measured Q301 voltages on schematic. What looks suspicious is that Q301 pin 8 has the same voltage as the adjacent pin 9, 2.3v.
I think pin 8 is the output for the 1st IF and pin 9 is the input for the 2nd IF block.
Do you have a capacitance tester or does you DMM measure capacitance?
Some cap testers will let you measure capacitance in circuit, but if you don't have one and your DMM can measure capacitance.
Try and remove one lead of C307 then measure the capacitance to make sure it is not shorted.
Also, examine the board trace to make sure there is not a solder bridge between pins 8 & 9.
I think pin 8 is the output for the 1st IF and pin 9 is the input for the 2nd IF block.
Do you have a capacitance tester or does you DMM measure capacitance?
Some cap testers will let you measure capacitance in circuit, but if you don't have one and your DMM can measure capacitance.
Try and remove one lead of C307 then measure the capacitance to make sure it is not shorted.
Also, examine the board trace to make sure there is not a solder bridge between pins 8 & 9.
I have already tested C 307 in circuit, it is not shorted and it reads 1 or just over in the board, if you need it tested out of the board i will need to remove board, does it make sense to remove the variable cap and test it ? removed C307 from board ,read 220,5 nf with esr tester seems to be non polar
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I checked resistors connecting to Q209 and Q210, found 2 that are way off but havnt removed them yet R260=12k, R262=22k, R263=560k, R264=2.2k, R265=2.2k, R259=5.6 Still looking for R301. Should i be removing the ones that are way off to test again?
Looks like R301 is on the schematic, but not on the board layout... maybe a design change. Q210E is directly connected to C249.
To test some of those resistors, it might be necessary to unsolder one resitor lead then measure the resistance.
First, check the resistor color code to see if the resistor value matches what is on the schematic. Sometimes there is a design change and a different resistor is substituted.
Compare your board traces to the layout in the SM. Does yours match?
There seems to be some other changes. R301 and C249 are connected in series, but the order is reversed.
To test some of those resistors, it might be necessary to unsolder one resitor lead then measure the resistance.
First, check the resistor color code to see if the resistor value matches what is on the schematic. Sometimes there is a design change and a different resistor is substituted.
Compare your board traces to the layout in the SM. Does yours match?
There seems to be some other changes. R301 and C249 are connected in series, but the order is reversed.
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C249 listed 47 uf reads 64.5 uf out of the board, Cap 248 lists at 22uf reads 27.6 uf R259 listed 5.6k reads 5.5 k, R262 lists 22k reads 22k, R264 lists 2.2k reads 2.2k R301 lists 2.6 k reads 2.6k All resistors colors match listed values.
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If we revisit this test, you might want to remove Q201 and Q204 and test.
- Red on Q201 base, Black on Q201 emitter - should read 0.45 to 0.9v. Swap leads and it should read OL.
- Red on Q201 base, Black on Q201 collector - should see a reading. Swap leads and it should read OL.
- Red on collector, Black on emitter - should be OL, reverse leads and should still read OL.
- Same test with Q204.
Saddly they both checked out perfect, I replaced the C249 with a 47 uf 16 vlt. with esr it was 68.5 uf
Thanks for all of your help with this. I will have the tuner checked with oscilloscope, also im going to try freeze spray on components while on to see if i can get a change. peteI'm out of ideas. Maybe your FM tuner needs alignment, but I'm not the one to instruct you on how to do it, sorry.