Eico 772W TX issue

[Crambone]

I picked up a near mint Eico 772W but has no TX, has ok receive. When keyed I can hear the relay slap but zero power output. I put my scope on the antenna out to see if any signal was getting past and see nothing.
any suggestions were to start? I did pop the relay cover off and cleaned the relay contacts. I’m going to pull the tubes and check them today.

 

[guitar_199]

Do you have the SAMS for this radio?

 

[BJ radionut]

All the info in the world my not help, as troubleshooting a KIT radio can be "interesting" not knowing whom assemble it.

 

[Crambone]

I found it, c42 that supplies negative voltage had gone open. Now onto the alignment.

 

[Crambone]

Do you have the SAMS for this radio?

Yes I found online, saved the day for me today

 

[BJ radionut]

I have VOL #7 Sams...Hard to scan those books without screwing the binders up...but if you still need a page or two...I'll help if I can!
All the Best
Gary

Sorry wrong radio VOL#4 was needed...I believe I have that one also...GL Gary

 

[guitar_199]

I found it, c42 that supplies negative voltage had gone open. Now onto the alignment.

If you can tolerate being "pestered"..... how did you track down/discover that bad cap in that position? What led you to it?

Tube RF final learning is getting to be hard to find...... thought I'd ask....

 

[Crambone]

If you can tolerate being "pestered"..... how did you track down/discover that bad cap in that position? What led you to it?

Tube RF final learning is getting to be hard to find...... thought I'd ask....

I began checking voltages on the tube pins per the schematic in the SAMS guide. It was the first tube I began to test. I was getting -.5vdc and knowing a bit about tubes I knew that wasn’t enough so I followed the issue to that capacitor. It was an old color coded cap that resembled a resistor. i tried to do a quick check in circuit and it was showing nothing but open. Once I replaced with a electrolytic 10mhz + to ground I had my negative voltage back. Prior to that I did replace all electrolytic sand wax paper. I also did in circuit test of every resistor hoping for a quick open/ shorted or high resistance. I only discovered 3 out of tolerance and all 3 where 10% gold bands that only showed a bit high but I replaced anyway. then I found a coil T5 had a bad connection internally and got me from -17db receive cutoff too -87db now. Next is TX alignment I ran out of time.

 

[guitar_199]

I began checking voltages on the tube pins per the schematic in the SAMS guide. It was the first tube I began to test. I was getting -.5vdc and knowing a bit about tubes I knew that wasn’t enough so I followed the issue to that capacitor. It was an old color coded cap that resembled a resistor. i tried to do a quick check in circuit and it was showing nothing but open. Once I replaced with a electrolytic 10mhz + to ground I had my negative voltage back. Prior to that I did replace all electrolytic sand wax paper. I also did in circuit test of every resistor hoping for a quick open/ shorted or high resistance. I only discovered 3 out of tolerance and all 3 where 10% gold bands that only showed a bit high but I replaced anyway. then I found a coil T5 had a bad connection internally and got me from -17db receive cutoff too -87db now. Next is TX alignment I ran out of time.

Thank you so very much..... I appreciate your taking the time to relay all of that. It took time and I appreciate it.

 

[BJ radionut]

Have you checked all the tubes yet??