It is currently Mon Mar 16, 2020 4:54 pm

All times are UTC - 7 hours



Post new topic Reply to topic  [ 51 posts ]  Go to page Previous  1, 2, 3, 4  Next
Go to page Previous  1, 2, 3, 4  Next
Author Message
Post subject: Re: 65 Pro Reverb with weak reverb
Posted: Wed Jul 03, 2013 4:32 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
By the looks of the plastic wing and style of metal base and holding tang, my guess is that is a Chinese made rectifier tube. Will check my sources when I get home.


Top
Profile
Fender Play Winter Sale 2020
Post subject: Re: 65 Pro Reverb with weak reverb
Posted: Wed Jul 03, 2013 8:30 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
Randy70065 wrote:
aclempoppi wrote:
Randy, hold on to that rectifier tube. I'm guessing it is a high quality 5URGB. The metal base and ST glass envelope tell me it's from the late '50's or '60's. I may be wrong!!! But maybe Beemer can give a better assessment of that tube. Art



I set it aside figuring I would make a nightlight out of it when I run out of things to do. I'll hang on to it. Thanks, Randy


+1

Throw nothing away.

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: 65 Pro Reverb with weak reverb
Posted: Wed Jul 03, 2013 8:07 pm
Offline
Hobbyist
Hobbyist
User avatar

Joined: Thu Jun 20, 2013 8:55 pm
Posts: 78
Location: South Texas
In the BIAS supply section the existing cap is a Mallory 50u\50v that looks original as dirt, but the PR schematic for the AA165 chassis shows it should have a 25u-50v. Should I correct it as per the schematic or just go back with a new 50u-50v? I ordered a 50u-50v before I checked the schematic. It looked original and I ordered to quick.

I also forgot to order the 7 caps for the circuit board to replace the single 25u\25v and three 25u+25u\25v caps, so I'll be placing another order anyway and can get another BIAS cap if needed.

Many thanks. \ Randy


Top
Profile
Post subject: Re: 65 Pro Reverb with weak reverb
Posted: Wed Jul 03, 2013 9:05 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
The 50/50 bias cap will work fine, no sweat. Be sure to note the reverse polarity when you install it.

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: 65 Pro Reverb with weak reverb
Posted: Thu Jul 04, 2013 6:58 am
Offline
Hobbyist
Hobbyist
User avatar

Joined: Thu Jun 20, 2013 8:55 pm
Posts: 78
Location: South Texas
Retroverbial wrote:
.... Be sure to note the reverse polarity when you install it.

Arjay


THANKS ARJAY!!!!!! I would have buzzed right over that. Glad you pointed that out.


Top
Profile
Post subject: Re: 65 Pro Reverb with weak reverb
Posted: Thu Jul 04, 2013 9:33 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
That's why we're here, sir.

Rawk on!

8)

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: 65 Pro Reverb with weak reverb
Posted: Sat Jul 06, 2013 12:32 am
Offline
Hobbyist
Hobbyist
User avatar

Joined: Thu Jun 20, 2013 8:55 pm
Posts: 78
Location: South Texas
I keep ordering parts! When does this end? :)

So far I've found 5 resistors that are out of spec by 20% or more, and one was added either by the PO or an amp tech.

Image

Now I'm not an amp tech by any stretch of imagination but the 220K resistor in the box above can't be the original. This 220K reads 152K and it looks like it's been scratched with something which makes reading the bands impossible. Not sure what happened but it doesn't match, and if I'm read'n it right this looks like part of the reverb send circuit. Wonder if I could be lucky enough to have found cause for the weak or near non-existent reverb problem? Probably not but I'll change it anyway.

I have another question if you have another minute. Can you tell me what volume POT this amp should have? The pot on the vibrato channel is not original, and the original on the clean side doesn't have a part number that I can find.

Many thanks!

Randy


Top
Profile
Post subject: Re: 65 Pro Reverb with weak reverb
Posted: Sat Jul 06, 2013 12:43 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
The schematic shows the volume pots on both channels to be 1Meg, audio taper. Tubes And More should have these in stock.

That 220K resistor looks to be part of the reverb recovery circuit (the "A" half of the 7025) -- it could very well be the primary source of the problem.

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: 65 Pro Reverb with weak reverb
Posted: Sat Jul 06, 2013 7:51 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Randy70065, just to be sure, you are pullling one leg of those resistors before reading?

Thanks! Good luck with the amp.


Top
Profile
Post subject: Re: 65 Pro Reverb with weak reverb
Posted: Sat Jul 06, 2013 1:48 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
BMW2002Ti wrote:
Randy70065, just to be sure, you are pullling one leg of those resistors before reading?


+1

It's imperative to isolate any component prior to taking static measurements.

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: 65 Pro Reverb with weak reverb
Posted: Sat Jul 06, 2013 2:39 pm
Offline
Hobbyist
Hobbyist
User avatar

Joined: Thu Jun 20, 2013 8:55 pm
Posts: 78
Location: South Texas
Did that but only on the resistors that looked discolored or odd in some way. Have no plans to pull more until the cap job is done, or unless I find some reason to keep digging. I'm hoping the idle hiss that I hear coming off standby is the result of the two busted and blistered filter caps.

Received part of my cap order today - one 50/50 bias cap. The rest should be shipped in 2-3 days. Woopie...


Top
Profile
Post subject: Re: 65 Pro Reverb with weak reverb
Posted: Sat Jul 06, 2013 3:32 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
Complete the cap job, replace that 220K resistor, bias it to some ballpark figure (34 to 35 mA) and see how it does.

(fingeroonies crossed)

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: 65 Pro Reverb with weak reverb
Posted: Sat Jul 06, 2013 8:04 pm
Offline
Rock Star
Rock Star
User avatar

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

What I do, is try to narrow down the suspect areas, while the amp is working (if it is...) before doing radical surgery. A good DVM, a schematic, and a wooden chopstick can save you a ton of time.

You know, if those are Allen-Bradley resistors --- you shouldn't need to change out many except those that have seen excessive current, due to malfunctions. Most burnt out puppies seem to be in the power rail and the output sections. Not in the input, gain stage, or PI sections.

You may find more leaky or needs-replacing caps in the coupling stages, depending on which cap manufacturer products are used in the amps.

Good luck with the amp! Keep us informed. :mrgreen:


Top
Profile
Post subject: Re: 65 Pro Reverb with weak reverb
Posted: Sat Jul 06, 2013 9:24 pm
Offline
Hobbyist
Hobbyist
User avatar

Joined: Thu Jun 20, 2013 8:55 pm
Posts: 78
Location: South Texas
Thanks BMW -

The actual count is 3 and not 5 as reported earlier. They are about 20% out of spec and probably a few others are as well. I'm not going to do any more surgery until I get the caps in and see where it goes from there.

The amp works and sounds strong everywhere except for the flabby bottom and the weak reverb which is all but gone, and it's got this annoying hiss when coming out of standby. It's a steady hiss with a very slight crackle in the background.

I need to start looking for an amp tech in central Louisiana who can bias the tubes. I've got a decent DVM and a box full of tools for small electrical work but that's it. I'd do it myself in a second if I had a bias meter or equivalent device.

Not sure where it came from but about a week ago I got a wild hair and decided to do something with the amp. It's been in the closet for 30 years because I either didn't have time or the desire to fix it up. I have no plans to sell it and it wasn't 100% original when I got it. Speakers were mismatched, reverb tank was changed, has a non OEM vol pot, one of the 470 resistors in the 6L6 socket has been changed and the top back cover is missing. I just want the original or near original tone.

Thanks to everyone for the helpful advice!

R


Top
Profile
Post subject: Re: 65 Pro Reverb with weak reverb
Posted: Sat Jul 06, 2013 10:13 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Randy, try a good contact cleaner (I like DeOxit GN5 or D5) on the sockets and pins of the tubes. This often solves hiss and popping issues.

You may need to tighten loose sockets. You need to drain the main power supply filter caps (with amp unplugged). I like a dental probe to tighten the brass tangs of the socket that hold the pins.


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 51 posts ]  Go to page Previous  1, 2, 3, 4  Next
Go to page Previous  1, 2, 3, 4  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: