telefunken: FM alignment and tuning indicator.
ID: 215917
? telefunken: FM alignment and tuning indicator.
16.Mar.10 02:14
0
Gentlemen,
I finished a chassis restoration of an Opus 7 USA. All electrolytic and paper type capacitors have been replaced. The AGC electrolytic C2 has also been replaced with the same value 2uf. All resistors checked with an ohm meter. The selenium rectifier has been replaced with a silicon bridge and a dropping resistor. The tuning indicator was quite dim and replaced with a fresh tube. All voltages checked and are reasonably close.
I completed a total alignment (am, sw and fm) and for FM used the AM signal generator method. The tuning indicator works great on AM but on FM it looks a bit over sensitive. The eye will hardly open when moving between stations.
With FM reception the indicator hardly opens between stations. It will open when the dial indicator is at the scale extreme (an area of no stations) and I unplug the FM dipole antenna. Then it opens up. I figure it may be my FM alignment technique.
Q1 - What alignment should I need to re-adjust (or start with) to yield a better tuning eye response? Or is there another potential problem?
Q2 - The schematic shows two 200k resistors in series to make up test point C. The alignment calls for 100k resistors. I used 100k resistors.
Thank you in advance for your time,
Paul
Found the Problem.
I over looked pulling a shield around the FM ratio detector tube V5.
C2 an electrolytic with + to ground was not replaced. Once replace the
Tuning eye now properly responds.
I checked the cap on a new cap meter and read 2.2 uf. So that did not tell
me any thing. I hooked it up (old C2) to the simple RF gen and O-scope ESR jig and
read about 8 ohms. Now I do not know if that is acceptable for a 2 uf electrolytic but the new 2.2uf 100v cap fixed the problem.
C2 an electrolytic with + to ground was not replaced. Once replace the
Tuning eye now properly responds.
I checked the cap on a new cap meter and read 2.2 uf. So that did not tell
me any thing. I hooked it up (old C2) to the simple RF gen and O-scope ESR jig and
read about 8 ohms. Now I do not know if that is acceptable for a 2 uf electrolytic but the new 2.2uf 100v cap fixed the problem.
Paul.
To thank the Author because you find the post helpful or well done.
This thread was moved automatically.
This question was moved automatically to the board "Talk" to get more possibilities for answers.
Moved from board »RADIO MODELS DISPLAYED« on 22.Mar.10 02:14 from automatically
still a question?
22.Mar.10 13:21
132 from 3306
Dear Paul,
is this still to be treated as a question? If not, then in future such cases it would be better to answer to your own post with the "information" flag set, instead of editing the original post.
Regards,
Mark
To thank the Author because you find the post helpful or well done.
I found the problem. Please disregard.
22.Mar.10 16:18
149 from 3306
Mark,
I was not sure how to treat answering my own question. Thanks for the tip.
Paul
Found the Problem.
I over looked pulling a shield around the FM ratio detector tube V5.
C2 an electrolytic with + to ground was not replaced. Once replace the
Tuning eye now properly responds.
I checked the cap on a new cap meter and read 2.2 uf. So that did not tell
me any thing. I hooked it up (old C2) to the simple RF gen and O-scope ESR jig and
read about 8 ohms. Now I do not know if that is acceptable for a 2 uf electrolytic but the new 2.2uf 100v cap fixed the problem.
C2 an electrolytic with + to ground was not replaced. Once replace the
Tuning eye now properly responds.
I checked the cap on a new cap meter and read 2.2 uf. So that did not tell
me any thing. I hooked it up (old C2) to the simple RF gen and O-scope ESR jig and
read about 8 ohms. Now I do not know if that is acceptable for a 2 uf electrolytic but the new 2.2uf 100v cap fixed the problem.
Paul.
To thank the Author because you find the post helpful or well done.
This thread was moved back manually because it received a valid answer.
Moved from board »* TALK - visible for members only« on 22.Mar.10 16:22 from Mark Hippenstiel