It is currently Mon Mar 16, 2020 2:55 pm

All times are UTC - 7 hours



Post new topic Reply to topic  [ 121 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6, 7, 8, 9  Next
Go to page Previous  1, 2, 3, 4, 5, 6, 7, 8, 9  Next
Author Message
Post subject: Re: 1965 Pro Reverb
Posted: Fri Nov 08, 2013 1:04 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Then, those are possibly weak 6L6GC tubes. Try another set and see what bias values, you get. The other possibility is resistors that have drifted in the bias supply. Or dried out caps in supply.


Top
Profile
Fender Play Winter Sale 2020
Post subject: Re: 1965 Pro Reverb
Posted: Sat Nov 09, 2013 4:38 am
Offline
Aspiring Musician
Aspiring Musician
User avatar

Joined: Sun Apr 14, 2013 4:41 pm
Posts: 764
Location: Sydney. Australia
Image


... located!

The other set of tubes made no change.


Top
Profile
Post subject: Re: 1965 Pro Reverb
Posted: Sat Nov 09, 2013 5:31 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Then, measure the 220k-ohm branch point or junction of the two grid-to-ground resistors -- v-shape junction on breadboard. Should read around (-) 50VDC with bias pot at midpoint.

Good luck. Keep us informed.


http://www.turretboards.com/layouts_sch ... layout.gif


Top
Profile
Post subject: Re: 1965 Pro Reverb
Posted: Sat Nov 09, 2013 11:58 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
NT, any luck with the VDC measurements in the bias supply?


Thanks!


Top
Profile
Post subject: Re: 1965 Pro Reverb
Posted: Sun Nov 10, 2013 12:29 am
Offline
Aspiring Musician
Aspiring Musician
User avatar

Joined: Sun Apr 14, 2013 4:41 pm
Posts: 764
Location: Sydney. Australia
Not yet ready to get into this; still doing a lot of reading and learning before I attend to bias circuit.

In the meantime I was able to fix the bacon frying/crackling problem by tapping the tubes and locating the V1 to be very noisy.

Herewith the offending Amperex in V1:


Image



When replaced with a new Tung-Sol 12AX7 the amp became so quiet I couldn't believe my ears.

I can only hope the amp will be this quiet when everything is done ..


Top
Profile
Post subject: Re: 1965 Pro Reverb
Posted: Sun Nov 10, 2013 12:48 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Nikola! That is an old Bugle Boy Amperex. Nice tube. But, hard to find any strong, quiet NOS these days.

I like the TS-RI 12AX7 for Fenders. Good luck with the amp.

Be interested in that bias, once you get around to it.


Top
Profile
Post subject: Re: 1965 Pro Reverb
Posted: Sun Nov 10, 2013 11:40 pm
Offline
Aspiring Musician
Aspiring Musician
User avatar

Joined: Sun Apr 14, 2013 4:41 pm
Posts: 764
Location: Sydney. Australia
Another interesting thing I found in the amp is this 5751 tube in V2 (tremolo chanel pre-amp tube). {Nothing else written on the tube to identify the brand}.


Image


I have replaced this tube with TS reissue 12AX7.

The result is a bit higher gain than 5751.

Looks like the 12AX7 has more pre-amplification than 5751.

Good to know :mrgreen:


Top
Profile
Post subject: Re: 1965 Pro Reverb
Posted: Mon Nov 11, 2013 11:24 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Nikola, that is a GE made 5751. GE used the acid etched dots as part of the date/factory site codes in the 1950-60's.


Top
Profile
Post subject: Re: 1965 Pro Reverb
Posted: Mon Nov 11, 2013 11:34 pm
Offline
Aspiring Musician
Aspiring Musician
User avatar

Joined: Sun Apr 14, 2013 4:41 pm
Posts: 764
Location: Sydney. Australia
BMW2002Ti wrote:
Nikola, that is a GE made 5751. GE used the acid etched dots as part of the date/factory site codes in the 1950-60's.



So, another dinosaur's tube :lol:

Apart from being quieter (less volume) than the newly installed 12AX7, this GE sound just fine. :wink:


Top
Profile
Post subject: Re: 1965 Pro Reverb
Posted: Tue Nov 12, 2013 2:18 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Nikola,

You know... that Bugle Boy tube looks like one of those "pinched waist" variety. It looks like the center portion of the glass envelope is narrower than the top or base areas. These are highly valued tubes.

Even if the tube is dead, just keep the thing, as a conversation piece. :lol:


Top
Profile
Post subject: Re: 1965 Pro Reverb
Posted: Fri Dec 13, 2013 12:45 am
Offline
Hobbyist
Hobbyist

Joined: Mon Mar 03, 2008 6:41 pm
Posts: 6
I've been all through your pic's of your amp. Great amp, wish mine still look like that, LOL. Any ways you seem to know alot about amps. I have the same amp set up as you do. From the info I've been getting, I have a 1966 Vibrolux reverb amp, with one 15in speaker. My two 6L6 gc RCA tubes have burn marks on the glass where the springs are at on the inside of the tube. All the other ones look ok but I know they should be check. Could that be the reason my amp is not working, the 6L6 tubs.

George


Top
Profile
Post subject: Re: 1965 Pro Reverb
Posted: Fri Dec 13, 2013 1:17 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
" Where the springs are at on the inside of the tube. "

Just outta curiosity, what "springs?" The heater coil or the grids? Photos would be nice, if you have any.

Thanks! :D


Top
Profile
Post subject: Re: 1965 Pro Reverb
Posted: Fri Dec 13, 2013 8:20 am
Offline
Hobbyist
Hobbyist

Joined: Mon Mar 03, 2008 6:41 pm
Posts: 6
BMW

Sorry but at the moment I haven't figured out how to upload pic on this forum yet. But I will keep trying. I don't know all the tec talk about these things, but I am guessing they are heater coil in the tubes. There are burn marks about the size for a quarter on each side of the tube where the hearter coils are. I just moved to North Carrolina and haven't found a place to have them check out. But thank you for trying to answer my question's.

George


Top
Profile
Post subject: Re: 1965 Pro Reverb
Posted: Fri Dec 13, 2013 9:21 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
barck88,

Are you talking about the silvered spots on the wall of the tube's glass envelope? Just above the getter rings? This is a getter blast from the getter ring. The tube manufacturer places specific metals onto the ring(s). Then, heat is applied, once the tube is finished. This causes the metal to evaporate or "blast" into the glass. The metal acts to trap any remaining oxygen left in the tube after most is mechanically pumped out.

See YouTube link to Mullard documentary (getter is explained around 29:40)

http://www.youtube.com/watch?v=GDvF89Bh27Y




Image


Top
Profile
Post subject: Re: 1965 Pro Reverb
Posted: Fri Dec 13, 2013 4:00 pm
Offline
Aspiring Musician
Aspiring Musician
User avatar

Joined: Sun Apr 14, 2013 4:41 pm
Posts: 764
Location: Sydney. Australia
barck88 wrote:
I've been all through your pic's of your amp. Great amp, wish mine still look like that, LOL. Any ways you seem to know alot about amps. I have the same amp set up as you do. From the info I've been getting, I have a 1966 Vibrolux reverb amp, with one 15in speaker. My two 6L6 gc RCA tubes have burn marks on the glass where the springs are at on the inside of the tube. All the other ones look ok but I know they should be check. Could that be the reason my amp is not working, the 6L6 tubs.

George




May I suggest you open another tread about your issue, (without hijacking mine), as I'm not yet finished with this tread and amp.

The story is I'm still waiting on the tech to become available and address a few things mentioned earlier in my posts. I wish I have BMW2002Ti's knowledge and expertize .. I bet he would sort this out in no time.


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 121 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6, 7, 8, 9  Next
Go to page Previous  1, 2, 3, 4, 5, 6, 7, 8, 9  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: