Vibrato and Volume

[PlayerElectone]

Something very strange just occurred. I have an A-105. When the vibrato tabs are ON, the volume is almost totally reduced to a whisper. When the vibrato tabs are turned OFF, the full volume returns. I am lost. Any suggestions?

[enor]

Yes, very common failure. If you search this forum you'll find lots of posts on the matter. The vibrato channel in your preamp has failed, and it often does in one out of a few very common ways.

[PlayerElectone]

I found some posts about this problem, but no one replied with any suggestions or solutions. :-(

[enor]

I did a quick search too and uncovered the following thread:

https://organforum.com/forums/forum/...p-with-vibrato

... among others, but that one contains all you need to know

[Jaim]

Swap the 6AU6's (V1 & v2). If the problem doesn't change, consult https://bentonelectronics.com/servic...-type-pre-amp/

Jim

[PlayerElectone]

Thanks to both of your for the info. I will try the tube-swap first.

[PlayerElectone]

First, I want to thank you all profusely for the suggestion to swap the 6AU6s. That's what makes this forum so awesome (for those of use who are electronically-challenged to a degree). I swapped them. The vibrato switches now work as they should. However (OK ... one last question) ... I do not detect any difference in the vibrato. It seems to work fine, and yet one of the tubes must have been bad??? Yes/No? Should I replace them? Or is that normal, that having switched them, everything is fine? Thanks for any info. BTW, all the tubes in this beast are marked "HAMMOND." Therefore, I assume they are all original. It had to be built sometime in the 60s. How remarkable that they have lasted this long. A tribute to good old American engineering back then. (Nothing lasts that long now including TVs, stereos, et al). Thanks - again.

[Jaim]

Possible the 6AU6 just needed to be re-seated. Hammond's don't drive the tubes to hard. Last a long time under those operating parameters. Enjoy the organ.

Jim

[PlayerElectone]

Awesome. Thanks, Jim. I'll save a few bucks and won't buy a replacement.

[PlayerElectone]

Well, after all my kudos, I turned on the organ today (the vibrato was fine after I switched the tubes), and it's back to the original problem. I assume I should replace BOTH 6AU6A tubes. So, I'm off on the hunt to buy vacuum tubes.

[enor]

The tubes aren't your problem - don't waste money on new ones. Since the problem has showed up again in the same way - but now with the tubes swapped - you've just proven that the fault lies elsewhere.

[PlayerElectone]

OK .. thanks. I guess it's time to call the repairman. :-I

[PlayerElectone]

I wanted to update my post from a long time ago. Our two Hammond./organ techs locally both have passed away, and the last one just retired, so any service has to come from a good distance. After trying to solve the issue myself, I bit the proverbial bullet and conctacted a tech in Cleveland. He was scheduled to come and provide service. In the meantime, I decided to try a last ditch effort. I puchased two new 6AU6A tubes on eBay (old stock but never used). I replaced the two on the pre-amp, and viola ... the vibrato works perfectly. Thinking it might be a fleeting fix, I have repeatedly powered up the organ, and it works every time. I'm holding my breath (and crossing all fingers) hoping this is a permanent fix. Service on organs is a real problem for us. (I'm in Toledo, Ohio) and we are tech-less. I really want to thank everyone who tried to assist with suggestions on here. This is a great resource - especially when there is no professional technical service readily available.