Uniden Washington Repair, Help!

[Number Nine]

Hi!, Real Novice here with promblems on old WASH.Radio (MB8719) Mike will "key" but no receive or transmit. 2 transistors sidebyside on rear heatsink are C2166 and C1969? Radio pwers up with lights. I have a matched set of 2SC2312 trans., would these be ok for replacement? Maybe I'm heading in the wrong direction. Any help would be great, THANKS!

[Rick]

Can you hear the relay click when key the mic and is the red TX LED come on? Are you running it off the built in power supply or ext power supply.

Rick.

[Number Nine]

Hi Rick ,have seen you help many people and THANKS for your time. No , I do not hear a relay click and trying to run on AC. NO transmit light, Mike could be faulty, yet I thought I connected correctly. (5pin) -Will check out all above. If radio "lights up" ,could I still have a bad power trans?(2SC1419) Thanks again for your time time.

[Rick]

If the radio does not light up check the collector of TR401 (2SD188) this is the one bolted to the heatsink it should be about 13 to 14 volts DC, I did not read you your message fully sorry. You will not hear the relay click has this version of the Washington does not have a relay. If you have a DC power supply try hooking it up do not forget to switch the radio over to DC. The power supply in the later Washington like your one was not very good, over the years I must of repaired 200 of there units. Hope this helps, let me know how you get on.

Rick.

[Number Nine]

Yeah no relay that I can find, and will check collector volts. Will try DC supply as well. Radio does "light up"on AC. Will get back to you and thanks for your help.

[fatdude1]

sounds like to me the finals are shot

[Rick]

sounds like to me the finals are shot

What with on RX and TX? It will probably be IC5 (MB3756) and or TR37 (2SC945) common fault on this radio.

This radio only has one final, which is TR41(2SC1969).

Rick.

[Number Nine]

I have voltage at TR301 C945 Q13YC, and D717 (bolt to Hsink) each in power subsection.Replaced C1969 but then put in 2SC1096 in place of C2166 (probably a bad idea). I hate to give up on this, it would be cool to get this runnin. Can IC5 MB3756 still be bought? And I guess I need a box of 2sc945's also. Thanks for any comments!

[Rick]

You need to treat each problem as you find it, it not a idea good just changing components because they look like they may be duff. You need to use logic (Spock). Most trouble with this radio is with bad power regulator and not with driver and final, but you say that the driver has been change for a 2SC1096, this will not do you need to change it to a 2SC2166 (Do not used one of your 2SC2312). But I think you need to treat the RX fault first the TX is easy, Your need to do some test and let me know what voltages you have at all the pins of IC5 (MB3756) and the voltages on the pins of TR37 in receive and transmit mode, if you let me know what I am asking you for we will get it working again.

Rick

[Number Nine]

Thanks Rick, Of course your right. I"ll stop shotgunning and stick to the voltmeter. Will replace 2166 ASAP and get readings on IC and TR37. I've found out this rig was put on DC with leads reversed- (had replaced blown protection diode). This board shows its age. I think I can look at a friends working model to confirm no butchering happen in this radio before I got it. Not a simple repair for the tinker, I wish I had proper test equipment and paid more attention in electronics class. Thanks for all your help. I'll keep posting as FACTS arise if anyone is interested in replying.

[zodiac]

If as you say, the leads have been reversed then you will be needing an audio IC as well but check the voltage regulator first as Rick says before fitting it.
Dave.

[Number Nine]

I have no volts at TR 37 C945 in RX or TX. Voltage present at IC5 MB3756 with unit just powered up, but not exact readings pin for pin-need better meter for readout. I can order new MB3756 and looking for C945 or sub.values

[Rick]

You could just replace IC5 (MB3756), IC4 (TA7222AP) Audio Amp and TR39 (2SC2166) Driver this should get it receiving and transmitting again, but this is only a guess, with out knowing the voltages just try replacing the above and see what gives you may be luck.

I do not know if you can read diagrams, I have tried to make as easy as possible.

Rick.

[Number Nine]

Thanks Rick,
the schematic I have is very poor even at high magnification. Again I see no voltage at TR37 but readings at IC5. I understand first things first. Better meter, replace 2SC2166,ck volts at TR's in power subsection,get exact readings at IC5,etc. Thanks for all the time you have spent on this.You guys amaze me; will keep posting as things develope.