It is currently Mon Mar 16, 2020 5:46 pm

All times are UTC - 7 hours



Post new topic Reply to topic  [ 20 posts ]  Go to page 1, 2  Next
Go to page 1, 2  Next
Author Message
Post subject: Silverface Bandmaster (AA1069)
Posted: Mon Jul 19, 2010 1:11 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
I redid a silverface Bandmaster this weekend. Anyhow, after replacing all of the electrolytes and some of the coupling caps. New tubes, etc... an interesting effect happened.

When the volume is at zero for both NORMAL and VIBRATO sections there is a faint "ticking" or motorboating sound. The minute I crank the volume past zero (either section) this "ticking" goes away. I've tried several 12AT7 (ECC81) in the reverb section. And several 12AX7 (ECC83) in the vibrato and other sections to no avail (changing tubes usually stopped low noise problems before). Sockets were all cleaned and tighten.

http://www.kbapps.com/audio/schematics/ ... a1069.html

Anyone familiar with this issue? Much Thanks!


Top
Profile
Fender Play Winter Sale 2020
Post subject:
Posted: Mon Jul 19, 2010 2:59 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Fri Feb 05, 2010 4:31 am
Posts: 14049
Location: Province de Québec, Canada
Begin to find from witch section it comes.

Start to remove your first preamp tube, the one at your right, see from the back of the amp.

If no more "ticking" you have to look in circuit before this tube. If "thicking is there, leave this first tube in place and remove the next tube.

Do that with all the tubes to find where in the amp, the "thicking" is comming.

Come back with news.


Top
Profile
Post subject:
Posted: Mon Jul 19, 2010 5:57 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Thanks! For the reply. I did this and the only small signal tube that stops the ticking is the PI tube. But, wouldn't this tube stop any noise anyway, since it drives the power tubes? Anyhow, any changes to the PI (different 12AT7 or ECC81) causes the same ticking noise.

I guess it could be the dropping resistor off B+ which powers the PI tube or some coupling cap on the PI?

Odd thing is that the ticking dissapears the minute I touch the volume control. The amp sounds fine when playing at any volume. Whether through the NORMAL or VIBRATO channels.

You know, I remember an Ampeg ReverboRocket I once redid awhile back (like 5 years ago). I tried replacing the OEM Westinghouse 7591's with new EH 7591. And a similar thing happened. There was this motorboating sound. But, it did not disappear with volume. It ended up that the Electro-Harmonix tubes coupled with each other, somehow. As when I replaced them with NOS 7591 the problem went away. If I replaced them with a variety of EH 7591 (I think I tried 3 diferrent pairs), then the motorboating returned.

Ever heard of 1990's vintage Svetlana (=C=) 6L6GC's coupling in this manner. BTW... I tried different power tubes and rectifiers with the same ticking results.


Top
Profile
Post subject:
Posted: Mon Jul 19, 2010 7:06 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Fri Feb 05, 2010 4:31 am
Posts: 14049
Location: Province de Québec, Canada
When you replace power tubes, did you do bias ajustment ?


Top
Profile
Post subject:
Posted: Mon Jul 19, 2010 7:13 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Sure did. To about 36 idle watts per tube. (440 VDC plate - cathode voltage) with about 41mA per tube. This amp seems to sound best at all volumes at this point.


Top
Profile
Post subject: Edit...
Posted: Mon Jul 19, 2010 7:15 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Sorry, didn't know how to edit my boo-boos. Meant 36 watts per both tubes.


Top
Profile
Post subject:
Posted: Mon Jul 19, 2010 8:15 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Fri Feb 05, 2010 4:31 am
Posts: 14049
Location: Province de Québec, Canada
It is good 41 ma per tube for bias. 440 X 41 ma = 18 watts/ tube

Can you explain your noise ? For me, motor boating is continious noise like rrrrrrrr and thicking is more like a clock ( one tic/ second, tic..tic..tic )


Top
Profile
Post subject:
Posted: Mon Jul 19, 2010 8:48 am
Offline
Rock Star
Rock Star
User avatar

Joined: Tue Aug 07, 2007 2:19 pm
Posts: 8827
I doubt it's the bias. It's probably something in the Vibrato circuit.

_________________
Life...... It's sexually transmitted and always fatal


Top
Profile
Post subject:
Posted: Mon Jul 19, 2010 9:16 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Fri Feb 05, 2010 4:31 am
Posts: 14049
Location: Province de Québec, Canada
Sure is not bias make that noise but BMW said he replace power tubes and bias make tremolo working.

But tremolo make noise like tic...tic... not motorboating


Top
Profile
Post subject: Vibrato "ticking" fix
Posted: Mon Jul 19, 2010 8:04 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
From another board: "It's the dressing around the vibrato tube (12AX7). If rerouting wire and resoldering components to the socket doesn't help, you can place an 0.01 mfd/600VDC cap across the 10M-ohm from the 12AX7 to ground. This will affect the tone, so use as last resort." Apparently, this was an issued service bulletin from Fender in the 1970's.

Thanks for your response. I wil try this "fix" this comoing weekend and report.

http://www.kbapps.com/audio/schematics/ ... a1069.html


Top
Profile
Post subject:
Posted: Mon Jul 19, 2010 8:53 pm
Offline
Professional Musician
Professional Musician

Joined: Fri Jun 26, 2009 6:53 pm
Posts: 2252
Location: Harvard IL
BMW, can you provide a link to the other board ? I recall reading something about this type of fix. Theoretically you could try a tube with a gain level as low as 70, and see what happens. Lead dress may or may not be the culprit. My '67 Band Master ticks a little, but I had an older Twin Reverb with the same lead dress that was quiet as a mouse. I would try different tubes, Sovteks always seem to knock down noise for me. Art

_________________
None of Us are free, if One of Us is chained !


Top
Profile
Post subject: " Ticking " amp...
Posted: Tue Jul 20, 2010 3:31 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
I tried maybe 4 different new 12AX7/ECC83 (reissued Tungsol 12AX7, 1970's Tungsram ECC83, 1960's Miniwatt ECC83, and 1950's RCA BP 12AX7)--- still same old ticking. Here's the link:

http://www.audioasylum.com/forums/tubed ... 86450.html


Top
Profile
Post subject:
Posted: Tue Jul 20, 2010 4:05 pm
Offline
Professional Musician
Professional Musician

Joined: Fri Jun 26, 2009 6:53 pm
Posts: 2252
Location: Harvard IL
Thanks, those sound like the same I had read about. Art

_________________
None of Us are free, if One of Us is chained !


Top
Profile
Post subject: Tremolo "Ticking"
Posted: Tue Jul 20, 2010 7:46 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Here's another link:

http://psg.com/~dlamkins/lamkins-guitar ... k-trem-fix


Top
Profile
Post subject:
Posted: Wed Jul 21, 2010 1:09 pm
Offline
Professional Musician
Professional Musician

Joined: Fri Jun 26, 2009 6:53 pm
Posts: 2252
Location: Harvard IL
Thanks, good reading ! I'm wondering why you want to do anything more to the Band Master, if the noise goes away when the volume is opened up ? Art

_________________
None of Us are free, if One of Us is chained !


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 20 posts ]  Go to page 1, 2  Next
Go to page 1, 2  Next

All times are UTC - 7 hours

Fender Play Winter Sale 2020

Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to: