The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

I agree with timrim, I would have a lot of broken radios if it weren't from some of the great help I've gotten here....A lot of people simply come here to get answers, then leave. On the other hand people like Defpom, Rick, Ramblingman and so on are a great asset to this board. As far as bad info, w...

The owner is hoping to get 27.555, his 2000 bit the dust in a thunderstorm. Just trying to get his very old backup going for him. Does anyone have the mod to do it? Thanks again Timrim!

Royce 1-619 Base 40 channel
M58473 PLL in the Royce "Sardine can" setup


Does anyone know if you can do a "switch mod" to this pll or does it need a different xtal?

Can't find any good pages on this pll chip

Thanks in advance and Merry Christmas to everyone here!

I may be wrong, but when you remove R44 the unit will adjust RX/TX together. VR5 or VR7 is not in the circuit anymore.

I had the same prob a long time ago, Rick corrected the procedure for me, look here in this forum...

http://www.radiomods.co.nz/forum/viewto ... =5274#5274

Early model 200's had some issues I've heard, but mine was the last board number made, bought it off the shelf (229.00 on sale)and sent it to cobra for the free tech updates. (No Cost but shipping) I was unfamiliar with the design so when I got it back, (I used it with good reports for about 6 month...

Have you checked to see if the mod limiter is intact, many times these are removed or "hacked" by less than skilled techs. You may simply be overdriving it without the limiter in place. Let us know what you find!

Sounds like a problem exsisted prior to the mosfet install. If someone replaced the final before, it most likely was frying them out prior to anything you did. Check for any other "hack" mods that might be causing the problem. jumped diodes, solder bypasses or even a bad solder joint or solder blob ...

Start simple, check the mic, is it working properly? Switch to PA and see if mic/audio is working, Let us know how it does....

You are right, I never meant everyone needs a linear, But a properly tuned radio can key 1~2watts and have forward swing to the proper limit of the final without the poor effect of a swing kit. It's like a kid with his first car, cutting off the muffler and believing it's a hot rod, it may be noisey...

With all the respect I can muster for a fellow radio tech, a swing kit is the poor man's way to create false watts. You may show wattage on an external meter but it is not viable wattage when you have created a radio that now spatters all over 6 channels. It is insane how some people think that a ra...

In the TR 467, The speaker is already grounded, it isn't a floating ground. running a resisitor to chassis ground will do nothing in this specific radio.

Dodge, That radio dosen't use a "needle" meter. 30 years didn't help this time!!!! Heh Heh.....

Dogem250, did you have too much coffee?!?!!? Heh Heh.... Your adding posts to just about every topic in here..... and to be honest, (well, in my opinion) many of them are very strange or incorrect answers. Many of them go against what most techs and long time users say or recommend.... No disrespect...

Thanks for the choke value, I replaced the choke, buttoned it all back up works great again! It's great to have the help you give, even when it turns out to be a simple fix after looking everywhere, I wouldn't have found for a long time without your direction. Now I owe you another pint...... LOL!

I believe it is a choke, The board is marked L404

Thanks for all the help Rick, I found the needle.... (in the haystack) R 113 open, replaced and static was gone, but still just a deak key, no audio... I did a headphone for audio on pin 6 like you said, no audio... followed it all the way back to the 5 pin mic board... The small black diode or chok...

OK correctly lifted legs and cap as suggested, no difference. Reinstalled parts: TR27 E 2.92/2.92 C 0.0/0.0 B 2.92/2.92 ( all are the same RX/TX) TR24 E- 0.0/0.0 rx/tx C- 0.0/0.0 rx/tx B- .70/0.4 rx/tx TR22 E- 0.5/.5 C-3.0/3.0 (when E lifted it is 7.0 RX/TX) B-1.10/1.09 emits a hum when tested in TX...

Damn just noticed I listed TR22 as TR27

I'll go back and lift leg of TR27 and give you the results. The voltages above that say TR27 are actually TR22....
My Bad eyesight, heh heh

IC4 starting at the back of the radio:

1 - 8.2
2 - 13.8
3 - 8.2
4 - 0.0
5 - 13.8 - on tx goes to 0.**
6 - 8.2 - on tx drops to 0.17
7 - 0.03
8 - 0.11 - on tx goes to 8.2

Checking other voltages now...

Lifted points as you asked, and pulled cap 232 leg, No change... When connected: TR24 E- 0.0/0.0 rx/tx C- 0.0/0.0 B- .70/0.4 TR27 E- 0.5/.5 C-3.0/3.0 (when E lifted it is 7.0 RX/TX) B-1.10/1.09 emits a hum when tested in TX with DVOM I'll try the other caps now, and get back, Thanks for the directio...

Thanks again Scott, I pulled a good one out of the other 148 and put it in. All problems went away. In fact to get it on freq before, I had to bottom out L23 to get AM right. Now I had to realign it and the L23 slug is back to around center. Audio is great on AM and SSB again. Freq also climbed abou...

Thaks Scott, I did look for a thread, must of missed it. I did lift pin 1 to see if there was voltage on the board, there wasn't . 13.8 coming from the chip. I don't have a spare, but I'll pull one from a working radio to test. Only problem noticed so far, audio real distorted, and on SSB there is a...

I have another Cobra 148, Had a terrible clarifier unlock job done to it: PC-412 Board PLL 8719 MB3756 pin 1 should have 8 volts, just as pin 3, but this radio is a 13.8 on pin 1. Is the chip bad? It had a very weird clarifier mod, I am putting it back to stock , and noticed pin 1 was high. ( The mo...

Just noticed I can get a swing above dead key by creating a squeal by touching the foil side of the board by the audio chip during key up, but no audio from the mic. Checked the mic gain switch, it's ok...

Board # EPT01481 3 Z PLL 8719 Cobra 148 GTL-F Problem No audio on TX, Good Dead Key no swing PA is just static Replaced Audio Chip - No change Picked up a 148 GTL-F, bought a new bezel and faceplate, worked great so only did the channel mod and talkback. About two weeks went by with no problems, the...