trc 457 not working need to replace all caps and power tran

[redfox 56]

Hi There

please let me know what are the Best replacement parts for thr trc 457 driver 2166 final 2312 I guess what about the voltage regulator and and tips on resistors change

I have a modified one that I think was pushing to high ,,,I want to make it work again but close to stock keeping the channels and also using a 2166 and 2312 finals

I ordered complete cap kit

what else the mods for putting back the amc limiter with 2 diodes is a plus

and channel selector is out now will not key up and chatters on ssb

will replace the relay

and hope after that it works

any thoughts on parts to replace to better the radio or just stock replacement parts any help is greatly thankful in advance .

this site seems very nice and Hello to everyone here

[pabxone]

The factory stock finals are 2SC1306 & 2SC1307 - A good reliable time proven pair - I'd only replace them if they are faulty and then only same for same or with 2SC2166 & 2SC1969 if the 1306 / 1307 are hard to get.
Don't buy or waste your money on any of the cheap c1306 c1307 c1969 or c2166 transistors that the 2 well know auction sites have advertised- They are almost always FAKES , At best they will work with low output and at worst they wont work at all - They are useless - Choose your supplier of RF power transistors carefully , If you are in the USA I would try contacting some of this sites sponsors to see what they have in stock.

C179 Tantalum is a common failure , I've had them go up in smoke and I've had a couple that have actually caught on fire when they failed - That will cause the relay to chatter on TX - Replace it with a 2.2uf 50volt electrolytic - Hopefully your re-cap kit includes replacements for all the Tantalum capacitors on board - There is about 6 tantalums and they are all unreliable at nearly 40 years old - best to replace them all.

Should be no need to change out the voltage regulator / switch 2SC1419 - It is fairly reliable and rarely fails - They can be substituted out with a TIP31C or TIP41C if they ever fail but a routine sub out would be of no point or gain if it hasn't failed.

The very first (And very early) production Cobra 138XLR / President Grant and other uPD858 radio's running the same chassis as the TRC457/TRC458 really punched out some power and audio to follow it up - however they were incredibly unreliable suffering from Driver / Final failures and production changes were brought on-line promptly to make them reliable (Fitting of Varistors sinked onto the driver and final to stop thermal runaway , bias changes etc) These changes are detailed in Cobra TSB001 -> TSB004 from memory and all are listed on Cbtricks dot Com
All production runs of the TRC457/458/449 have the design changes added in original production - You could however reverse engineer the running changes out by doing the exact reverse of what TSB001 -> TSB004 are telling you to do - BUT I strongly suggest that you DON'T.

The AMC and anything to do with modulation on any 858 chassis ---> LEAVE IT ALONE ~ RETURN IT TO FACTORY BUILT - Make sure any modifications such as listed in SECRET CB and Etc are removed and the board is returned to original. The 858 chassis audio is one of the best you will ever find straight out of the box

Unit 399 has written a pretty extensive insight into the 858 chassis & if you are going to do any mods to an 858 chassis - I'd strongly suggest you follow his methodology as it is sound and reliable - It's worth having a read at bigstrap DOT tripod DOT com

You may not need to replace the Relay , They rarely fail other than the coil burning out and then it won't energise - Yours is chattering so it's not burnt out - They can get dirty switching contacts But they can be "Carefully" cleaned with Microscrub or a very fine burnishing tool - CRC switch lube / Contact cleaner could be used But I'd suggest Microscrub is a better option.

73,
Mark

[redfox 56]

THANK YOU FOR YOUR ADVICE

I will do what you said and hope it works I am not sure if I mentioned the channel is out to no lighted

is this a cap issue as well?

so far can receive no tx ssb chatter on the relay

and finals look original with the heavy plastic like material behind them

will use mica with heat sink compound

radio was modified at some point has so many things jumped lol

will try and put amc back and just get her running again but overall not bad shape clock still works lol

-- 16 Mar 2016, 15:35 --

I ordered the sk3620 cross nte 331 for 6 bucks ebay

waiting for the 2166

and the 2312

I replaced the regulator with a nte 152 since it was a hack job last replacement

now after that I will replace all the electolytics and see if it at least works lol

I will wait for the parts about 2 weeks I think then we will see if she keys up so for no led for channels

clicks like it wants to key up on am and sideband but nothing no watts

could be the driver and final ?

but I do have a 23 channel set I could take them out of but thinking to wait

there are a lot of caps big job will be doing this little at a time since my back and leg can not take to much time on the table

Broke my knee in 4 pieces wired and screwed so that s why I have the time to play with this radio it is my friends he did not trust anyone with it besides parts are tough

I have a 138 xlr mobile too so plenty of parts I hope

any thoughts of why it is dead lol long shot here

-- 16 Mar 2016, 16:20 --

Hello

Has anyone had a no tx no side band on a trc 457

I did replace one 2.2 50 vlt cap

now no chatter on ssb in relay

I have ordered some parts since its very old thinking new driver new final new regulator

and has there been any other failing parts I should know about have a cap kit will replace all I have

maybe the caps are junk

and no channel display light

any thoughts?

[pabxone]

Start off with just replacing C179.

I suspect that is causing the NO TX and the relay chatter.

There is a possibility - Very slight it could be pulling the voltage down and causing the LED display to go out.

[sonoma]

C179 causes more problems in SSB mode , do the cap mods 1st before you go swapping parts that may or may not be bad. also there is a diode just in front of the relay towards the front of the radio that can short and cause the relay to chatter. forget the number on it but a resister right by it will get hot if the diode is bad alson.

[redfox 56]

i REPLACED THE CAP C179 NO MORE CHATTER BUT NO WATTS NO TRANSMIT SSB IS SAME AS AM CLICK STABLE BUT NO TRANSMIT STILL NO LED

-- 16 Mar 2016, 18:52 --

I noticed a part uhic 005a de 128 near the 858 looks melted

I may have found the problem I do not think it should of melted into the caps near it lol

anyone have any idea were to get it ?

Thanks Guys

[pabxone]

i REPLACED THE CAP C179 NO MORE CHATTER BUT NO WATTS NO TRANSMIT SSB IS SAME AS AM CLICK STABLE BUT NO TRANSMIT STILL NO LED

I noticed a part uhic 005a de 128 near the 858 looks melted
I may have found the problem I do not think it should of melted into the caps near it lol
anyone have any idea were to get it ?

Thanks Guys

UHIC005 is the HYBRID VCO module and it NORMALLY looks bulged and odd on one side with internal components inside (The side without the writing) so that is normal.

Is receive OK and just No Transmit and the LED's not lighting being the faults now ?

-- 17 Mar 2016 18:51 --

If RX is OK but NO TX and NO LED Display is the fault now try looking here :-

TR25 (2SC1419) Regulator / Switching transistor is in the circuit for both the Negative power feed for the LEDs and the AM TX power - It's a good starting point to check out (It's the large transistor on the rear of the board about 3 inches to the Right of the 2 finals)
It should have 7 volts on the base , 12.7 volts on the collector and 6.2 volts on the emitter.
TR26 is right in front of TR25 and should have 4.5 volts on the base , 7 volts on the collector and 3.8 volts on the emitter - If the 3.8 volts is missing Zener Diode D26 is blown. Also if any voltages on these 2 transistors are seriously wrong C102 (220uf Electrolytic) is probably faulty.

Check Zener diode D44 banded end for 9 Volts
Check Zener diode D24 banded end for 9 Volts
Check Zener diode D28 banded end for 9 Volts
Check Zener diode D25 banded end for 7.5 Volts
Someone else mentioned these Zeners - They do blown and can cause some 2 watt resistors near the Relay to get VERY HOT (You will burn your finger if you touch them) - You will likely smell the heat coming off the resistor heating the plastic in the wiring loom above the resistor.

TR24 (The other 2SC1419) check it for 9 Volts on the base , 13 volts on the collector and 8.2 volts on the emiter - if these voltages are wrong most likely C98 & C99 (both electrolytic capacitors) are faulty or D24 is blown or TR24 is blown.

Check also the CB/PA switch in NOT binding or sticking - These switches tend to gum up and jam in one position but I've seen them jammed 1/2 way operated and that would cause this fault - Hit the switch with a Blast of CRC switch lube and operate it a LOT whilst it is still wet with the cleaner to free it up

[redfox 56]

Thank you so much I will try all of what you said and with hope it will run again .

Very kind of you to tell me your thoughts .

I will post my findings as well

Thanks again

[sonoma]

you can check the diodes with a meter and if one is bad change it out. I would be careful until you get the radio capped. if a diode is bad a shorted cap can cause it to fail again. since you have the caps ordered I would check the diodes then change out the caps before you keep trying to get it to run or you could do more damage to other parts that are not bad yet.
change all the caps check the diodes then fire it up to see where you are at. as old as the radio is the caps are failing for sure. pabxone gave you a lot of good info so far.

[redfox 56]

thanks guys I am replacing the caps and I have to say what a pain in the neck lol

but I will be changing them out a few maybe 6 a day my back is very bad and knee was broken in december so taking it easy but after I swap out the caps then check some voltages it is like new when I am done lol

so many caps ahhhh and well I will stay with it .

Thanks for the help everyone .
Joe

-- 18 Mar 2016, 12:09 --

you can check the diodes with a meter and if one is bad change it out. I would be careful until you get the radio capped. if a diode is bad a shorted cap can cause it to fail again. since you have the caps ordered I would check the diodes then change out the caps before you keep trying to get it to run or you could do more damage to other parts that are not bad yet.
change all the caps check the diodes then fire it up to see where you are at. as old as the radio is the caps are failing for sure. pabxone gave you a lot of good info so far.

thanks for the information

Tr 37 is missing

also can not find d 24 ?

looks like it may of been there before have any idea what it was

-- 18 Mar 2016, 12:11 --

tr 37 is missing and looks like it may of been there before ..

D 24 can not locate have D 26

still doing caps long job

-- 19 Mar 2016, 16:31 --

i REPLACED THE CAP C179 NO MORE CHATTER BUT NO WATTS NO TRANSMIT SSB IS SAME AS AM CLICK STABLE BUT NO TRANSMIT STILL NO LED

I noticed a part uhic 005a de 128 near the 858 looks melted
I may have found the problem I do not think it should of melted into the caps near it lol
anyone have any idea were to get it ?

Thanks Guys

UHIC005 is the HYBRID VCO module and it NORMALLY looks bulged and odd on one side with internal components inside (The side without the writing) so that is normal.

Is receive OK and just No Transmit and the LED's not lighting being the faults now ?

-- 17 Mar 2016 18:51 --

I can not locate D 24 ?

even on a schematic its not easy lol

but trc 37 looks like it was removed also seems to tie into the led display

If RX is OK but NO TX and NO LED Display is the fault now try looking here :-

TR25 (2SC1419) Regulator / Switching transistor is in the circuit for both the Negative power feed for the LEDs and the AM TX power - It's a good starting point to check out (It's the large transistor on the rear of the board about 3 inches to the Right of the 2 finals)
It should have 7 volts on the base , 12.7 volts on the collector and 6.2 volts on the emitter.
TR26 is right in front of TR25 and should have 4.5 volts on the base , 7 volts on the collector and 3.8 volts on the emitter - If the 3.8 volts is missing Zener Diode D26 is blown. Also if any voltages on these 2 transistors are seriously wrong C102 (220uf Electrolytic) is probably faulty.

Check Zener diode D44 banded end for 9 Volts
Check Zener diode D24 banded end for 9 Volts
Check Zener diode D28 banded end for 9 Volts
Check Zener diode D25 banded end for 7.5 Volts
Someone else mentioned these Zeners - They do blown and can cause some 2 watt resistors near the Relay to get VERY HOT (You will burn your finger if you touch them) - You will likely smell the heat coming off the resistor heating the plastic in the wiring loom above the resistor.

TR24 (The other 2SC1419) check it for 9 Volts on the base , 13 volts on the collector and 8.2 volts on the emiter - if these voltages are wrong most likely C98 & C99 (both electrolytic capacitors) are faulty or D24 is blown or TR24 is blown.

Check also the CB/PA switch in NOT binding or sticking - These switches tend to gum up and jam in one position but I've seen them jammed 1/2 way operated and that would cause this fault - Hit the switch with a Blast of CRC switch lube and operate it a LOT whilst it is still wet with the cleaner to free it up

[pabxone]

thanks guys I am replacing the caps and I have to say what a pain in the neck lol

tr 37 is missing and looks like it may of been there before ..

D 24 can not locate have D 26

still doing caps long job

/quote]

TR37 may not need to be there it is a part of the LED dimmer circuit used in the TRC449 but the TRC457/458 does not have a dimmer circuit.
But the SAMs Manual does show TR37 as being in place in the TRC457/458 - TR37 should be a 2SA719. (I don't have an original Radio Shack TRC457/458 circuit diagram only a TRC449 to refer to)
In theory if there is a strapping wire link from TR37 base to emitter on the PCB the transistor likely doesn't need to be there ?
(This may explain your lack of an LED display TR37 missing? )

D24 will be just below the middle of the relay next to R111 - The thick wiring loom above it will be hiding it from view.

I have a TRC457 here - and since I cant seem to find a TRC457 diagram anywhere - I'll go and pull it apart now and see if there should be a TR37 in place.

-- 20 Mar 2016 11:34 --

OK on a visual inspect of a TRC457 I have here -
TR37 (2SA719) and VR17 are both in place as per the SAM's manual.
On the TRC457 the LEDS can be dimmed or brightened by turning VR17 on the PCB even though there is no dimmer control on the front panel, TR37 is part of that circuit along with TR36.

The question is why was TR37 removed ?

[redfox 56]

Thank you I found d 24 lol and I have ordered some parts and will be replacing them and I thought this was supposed to be there and yes I found it missing but the people before me had there hands in it .

I was given this to fix for a friend I have known for 25 years he bought it not working for 50 bucks is what he told me .

so I have found the parts d 24 d 26 and tr 26 I may replace them since I am in it this far lol all caps almost done wow so many and I ordered new final and driver
2166 and a 2312 I do have a trc 57 that still has the 2166 and a 1969 I may take them out not sure 23 channel radio kinda nice .

I do have some schematics on trc 457 I will see if I can load it to a thumb drive then email you the prints or give me a address `to send them to you .

it is page size thinking of going to staples to blow it up

but I kinda thought after looking at the schematic tr37 was needed and 2sd325 tr36 is not present as well

[pabxone]

but I kinda thought after looking at the schematic tr37 was needed and 2sd325 tr36 is not present as well

TR37 (2SA719) & TR36 (2SC1419) are definitely needed - Without them there will be no power feed to the LED display.

It looks like some has used this rig as a parts donor at some stage?

2SC2166 and 2SC2312 will be fine as a Driver / Final pair - I wouldn't be in a rush to part down another radio just to get a 2SC1969

[redfox 56]

WELL THANKS TO ALL FOR YOUR HELP !

Now I am waiting for the 9 vlt zener diodes 7.1 zener and 2 types of transistors and one other transistor type forget the numbers but when I found d24 it was broken in 2 pieces.

alll caps are done waiting for parts mostly nte and sk parts ordered .

those caps were going to be the death of me . OMG so Many ... now when I get the diodes and transisters I can not wait to see if she works ...but I told my friend Never again lol, no more fixing radios that I have no idea what was done to it ....lol

I am hoping it will work and I can get it off my work table ,,:)

If after all this it does not work I will cry ,,,,,ahhhh

but It looks good so many dead solder joints I fixed and now it will feel good to see it work again .

I guess some parts from various places in usa some from china most are nte diodes and transistors I do have two spare 858 pll chips so even if thats is gone I may still be able to fix it .

I bought 2 of them and 2 8734 when about 25 years ago they were stop making radios with the chips but even 02A were nice 8719 cobra and some others .

but I guess this guy loves this radio not sure why to me its okay but when I get it running maybe it will surprise me .

practically rebuild ,,, what we do with our time lol

Thanks Joe

-- 31 Mar 2016, 10:03 --

I replaced all these parts and I have no receive or tx he said it never received as well

so with all that work now I have to think what else could the pll 858 be bad

relay clicks no chatter

lights up just will not key up

replaced the final and driver 2166 1969 out of the 23 channel radio I had

regulator nte 152

never replaced the relay ?

but I am thinking its is a transistor or diode problem will have to start checking them out .

I have worked on a few other so I would tty and Keep sane lol.

old presedent jackson export model seems nice my brother had it as a base nice radio but am is a little weak 80 percent modulation . limiter was taken out for sideband and am someone changed a resistor and took out two caps seems to run ok . nice all black .

worked on a cobra 148 from the phillipines nice radio never was touched still has no channels in it .

but this base 457 is killing me I have another pll should I try that

well I need to make sure its not another part any ideas are greatly appreciated lol

I here so many loose tx and rx why the relay would be my first thought regulator 2nd but both gone what is it please >>>>>>>

-- 31 Mar 2016, 18:07 --

Hello
I have no tx or rx and can not find d44 lol

HELP ME LOL

thanks guys I am replacing the caps and I have to say what a pain in the neck lol

but I will be changing them out a few maybe 6 a day my back is very bad and knee was broken in december so taking it easy but after I swap out the caps then check some voltages it is like new when I am done lol

so many caps ahhhh and well I will stay with it .

Thanks for the help everyone .
Joe

-- 18 Mar 2016, 12:09 --

you can check the diodes with a meter and if one is bad change it out. I would be careful until you get the radio capped. if a diode is bad a shorted cap can cause it to fail again. since you have the caps ordered I would check the diodes then change out the caps before you keep trying to get it to run or you could do more damage to other parts that are not bad yet.
change all the caps check the diodes then fire it up to see where you are at. as old as the radio is the caps are failing for sure. pabxone gave you a lot of good info so far.

thanks for the information

Tr 37 is missing

also can not find d 24 ?

looks like it may of been there before have any idea what it was

-- 18 Mar 2016, 12:11 --

tr 37 is missing and looks like it may of been there before ..

D 24 can not locate have D 26

still doing caps long job

-- 19 Mar 2016, 16:31 --

i REPLACED THE CAP C179 NO MORE CHATTER BUT NO WATTS NO TRANSMIT SSB IS SAME AS AM CLICK STABLE BUT NO TRANSMIT STILL NO LED

I noticed a part uhic 005a de 128 near the 858 looks melted
I may have found the problem I do not think it should of melted into the caps near it lol
anyone have any idea were to get it ?

Thanks Guys

UHIC005 is the HYBRID VCO module and it NORMALLY looks bulged and odd on one side with internal components inside (The side without the writing) so that is normal.

Is receive OK and just No Transmit and the LED's not lighting being the faults now ?

-- 17 Mar 2016 18:51 --

I can not locate D 24 ?

even on a schematic its not easy lol

but trc 37 looks like it was removed also seems to tie into the led display

If RX is OK but NO TX and NO LED Display is the fault now try looking here :-

TR25 (2SC1419) Regulator / Switching transistor is in the circuit for both the Negative power feed for the LEDs and the AM TX power - It's a good starting point to check out (It's the large transistor on the rear of the board about 3 inches to the Right of the 2 finals)
It should have 7 volts on the base , 12.7 volts on the collector and 6.2 volts on the emitter.
TR26 is right in front of TR25 and should have 4.5 volts on the base , 7 volts on the collector and 3.8 volts on the emitter - If the 3.8 volts is missing Zener Diode D26 is blown. Also if any voltages on these 2 transistors are seriously wrong C102 (220uf Electrolytic) is probably faulty.

Check Zener diode D44 banded end for 9 Volts
Check Zener diode D24 banded end for 9 Volts
Check Zener diode D28 banded end for 9 Volts
Check Zener diode D25 banded end for 7.5 Volts
Someone else mentioned these Zeners - They do blown and can cause some 2 watt resistors near the Relay to get VERY HOT (You will burn your finger if you touch them) - You will likely smell the heat coming off the resistor heating the plastic in the wiring loom above the resistor.

TR24 (The other 2SC1419) check it for 9 Volts on the base , 13 volts on the collector and 8.2 volts on the emiter - if these voltages are wrong most likely C98 & C99 (both electrolytic capacitors) are faulty or D24 is blown or TR24 is blown.

Check also the CB/PA switch in NOT binding or sticking - These switches tend to gum up and jam in one position but I've seen them jammed 1/2 way operated and that would cause this fault - Hit the switch with a Blast of CRC switch lube and operate it a LOT whilst it is still wet with the cleaner to free it up

-- 01 Apr 2016, 17:05 --

Hi everyone thank you for the helpful tips still no rx or tx can not imagine why

going to start to check all diodes

and the 2 blue capacitors near the 858 chip


you think the chip is bad maybe ? do they go ?

were is d 44 lol

-- 01 Apr 2016, 17:05 --

Hi everyone thank you for the helpful tips still no rx or tx can not imagine why

going to start to check all diodes

and the 2 blue capacitors near the 858 chip


you think the chip is bad maybe ? do they go ?

were is d 44 lol

-- 03 Apr 2016, 12:57 --

Radio now has receive and no tx still

But happy its able to receive now I will go over all solder points checking for anything cracked some dead solder joints

but thanks for the help so far

D44 were exactly is this diode ?

can not locate it still no digits on chanel display key mike and meters change color no power out put not worried about the channel display just want it to key up lol

Thank you

Joe

-- 03 Apr 2016, 13:01 --

Radio... has receive just no tx but happy to get the receive 50 percent there

d44 anyone have any idea were it is lol

but the radio seems to be coming alive mod channels working

but no tx why ahhhhh,,,,,,

lol
Thanks Joe

i REPLACED THE CAP C179 NO MORE CHATTER BUT NO WATTS NO TRANSMIT SSB IS SAME AS AM CLICK STABLE BUT NO TRANSMIT STILL NO LED

I noticed a part uhic 005a de 128 near the 858 looks melted
I may have found the problem I do not think it should of melted into the caps near it lol
anyone have any idea were to get it ?

Thanks Guys

UHIC005 is the HYBRID VCO module and it NORMALLY looks bulged and odd on one side with internal components inside (The side without the writing) so that is normal.

Is receive OK and just No Transmit and the LED's not lighting being the faults now ?

-- 17 Mar 2016 18:51 --

If RX is OK but NO TX and NO LED Display is the fault now try looking here :-

TR25 (2SC1419) Regulator / Switching transistor is in the circuit for both the Negative power feed for the LEDs and the AM TX power - It's a good starting point to check out (It's the large transistor on the rear of the board about 3 inches to the Right of the 2 finals)
It should have 7 volts on the base , 12.7 volts on the collector and 6.2 volts on the emitter.
TR26 is right in front of TR25 and should have 4.5 volts on the base , 7 volts on the collector and 3.8 volts on the emitter - If the 3.8 volts is missing Zener Diode D26 is blown. Also if any voltages on these 2 transistors are seriously wrong C102 (220uf Electrolytic) is probably faulty.

Check Zener diode D44 banded end for 9 Volts
Check Zener diode D24 banded end for 9 Volts
Check Zener diode D28 banded end for 9 Volts
Check Zener diode D25 banded end for 7.5 Volts
Someone else mentioned these Zeners - They do blown and can cause some 2 watt resistors near the Relay to get VERY HOT (You will burn your finger if you touch them) - You will likely smell the heat coming off the resistor heating the plastic in the wiring loom above the resistor.

TR24 (The other 2SC1419) check it for 9 Volts on the base , 13 volts on the collector and 8.2 volts on the emiter - if these voltages are wrong most likely C98 & C99 (both electrolytic capacitors) are faulty or D24 is blown or TR24 is blown.

Check also the CB/PA switch in NOT binding or sticking - These switches tend to gum up and jam in one position but I've seen them jammed 1/2 way operated and that would cause this fault - Hit the switch with a Blast of CRC switch lube and operate it a LOT whilst it is still wet with the cleaner to free it up

-- 04 Apr 2016, 22:15 --

I found all the zener diodes now I think I need 5 wat replacements

I used 1 watt and I think they are not good enough

the 2 resistors are getting hot near the relay

I have receive no transmit

I will order new diodes and need to replace the cooked resistors

if I can get it working It will be such a smile .

But for now I hope the caps I used are good enough too

but it is receiving nice