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858 president Washington needs saving.

2

200eazy

Member
Sep 23, 2017
27
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Ok. So I’ve been trying to save this radio for a couple months now. It belongs to a good friend of mine so I’d like to finish it for him. It came to me with no rx, tx, or pa. After opening the case it was clear to see it had been hacked on for a channel mod, but never finished. I removed the obvious mods and put it back to stock. Recapped the whole radio and still nothing. On the board the ground trace close to ic has gotten hit and the trace lifted. I installed a copper wire to bridge the burnt section and replaced ic3. Still no audio at all. R113 is a 150ohm 1 way metal foil resistor. Turn the radio on for a few min and it get too hot to touch. Reconnected the cut pin traces from the 858 chip and still nothing. Some transistors has been clipped and several diaods as well. Replaced all of them and still nothing. The only sound you get is the speaker pop when turning the radio on or off. Also the relay is working so it is keying. Light on from shows tx but no meter deflection. Final and driver checked good. Please any help is greatly appreciated.
 

I've had to replace the 858 PLL because of a bad channel hack mod artist.
All I'm saying is that it is possibly fried if you cannot test the PLL - which you must do.
RF Parts still carry them - IIRC.

The ribbon cable from the PLL area to the channel selector can have a problem with that socket; radio will act dead. Fixed two radios alone by just cleaning those contacts on the cable and the corresponding socket; wan't easy nor pretty. Must be VERY careful; or else you will ruin them too easily if great care isn't taken.

The relay should be carefully cleaned as well. No sandpaper or file should be used on its contacts; just clean paper/card w/contact cleaner until no residue shows on the paper.

Hope that helps.
 
I’ve got another 858 chip I can try. I’ll check out the ribbon and the connector as well. Any idea as to why r113 is getting so hot? I know some heat is to be expected but this seems excessive to me. 13.8 volts measured across the joints.
 
check some of the diodes in the section with the relay and R113. one of them can short and heat up R113. numbers are
D25, D27, D28.. may be a few more right in that area around the relay shorted causing a problem. if you do not have a schematic for this radio the trc-449 will work for you to compare parts.
 
Think I would test the PLL before just yanking it out and putting even more stress on the foil/traces.

I would go with sonoma's suggestion about the diodes for the heat problem - first.

I would also test the ribbon cable before messing with the PLL and after you deal with the heat issue on the resistor . . . JMHO . . .
 
Last edited:
I’ll check the pll. Will d24 cause r113 to get hot? Will also be checking r112 tonight.
I’ve been using the 449 manual to get it this far.
 
Make sure all of the crystals are properly seated in their sockets, and the sockets are well soldered. This can also cause issues with no TX/RX. There's also a chance that the 10.240 crystal may be bad.


~Cheers~
 
Like sonoma said; check all of the diodes that share that same line/circuit with R113. D27 is a in4003 diode for protecting the relay (IIRC). D25 is a 7.5v zener diode, so if bad you will need to get one. Since it is a zener diode, you cannot just throw any diode in there and expect it to work. D28 is a 9.2v zener; same thing goes. D26 is a 3.7v zener diode; but doesn't share that circuit - just an example. Dunno what you know about components, just pointing these facts out to those reading along.

Was this radio exposed to reverse voltage?
 
Just wanted to express a big thank you to Sonoma and our own Robb (Rest in peace) As I was very close to calling it quits after spending endless hours of trying to find out why stuff was not working on that base President Washington. Made a thread a week and a half ago and it wasnt until last night I poured in hours trying to track down the issue... Today was the day I noticed R113 was getting HOT to the touch, like unbearable.

It progressively got worse, and I accidentally shorted the 13v to ground which blew the fuse of the external 12v on the power cord, but replaced it. Once turning it back on, R113 said no more and let the smoke out.. Thanks to this thread. I typed it in google search one more time about r113 and President Washington getting hot, and it brought me here. I did try out the other diodes and resistors as suggested by Sonoma, but they all checked out ok with no short. Then... Thats when it hit me... There was that ONE diode at D24.... And wouldnt you know, the bastard is SHORTED out! That may of been the source of this entire headache all along. I will need to find a replacement diode. According to the TRC 478's service manual, it does show as 1N4739A. Can someone verify it or maybe another radio I can yank the Diode from? I do have a broken Cobra 139 SSB 23 channel radio if that could work taking parts from.


I will report back on the original thread I did when I can find a replacement diode and see if power comes back or if something smokes once again. Thanks again.
 

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