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Some gut shots from my new '67 Twin Reverb (Update at post #28, back from tech.)

olin

Silver Supporting Member
Messages
627
I know you've seen better....but have you seen worse?? :omg

I know it's going to need some work but I couldn't resist.

Here's what I think I know about:

The reverb and the choke all date to '66 (606-6-30 and 606645).

The power transformer dates to early '67 (606707).

The speakers are JBL D120Fs but I haven't had much luck finding any codes and the serial #s are very hard to read. There's a sticker (see picture) but I don't know what it means.

As you can see in one picture, the tube chart is a goner.

The code on chasis is "A 07816" which also dates it to '67.

What do you make of these pictures? Should I expect a lot of repair and restoration to be needed? She sounds pretty good but it does have issues. It's not as loud as it should be and it does make its share of strange pops, hisses, flutters and warbles. ;)

I'm hoping, with a little TLC from a qualified tech, she can be a good one.






 
Last edited:

drbob1

Gold Supporting Member
Messages
29,181
Don't know what the sticker on the JBL means, but they look worn but righteous from this side. Pics of the cone side could help us determine if they've been reckoned.

Definitely going to need pics of the inside of the chassis and the PS caps to tell you how much work it's going to need. The chassis itself is very clean, don't be too worried about some rust on the outside of the transformer, it's pretty common...
 

olin

Silver Supporting Member
Messages
627
Don't know what the sticker on the JBL means, but they look worn but righteous from this side. Pics of the cone side could help us determine if they've been reckoned.

Definitely going to need pics of the inside of the chassis and the PS caps to tell you how much work it's going to need. The chassis itself is very clean, don't be too worried about some rust on the outside of the transformer, it's pretty common...
Thanks Bob. That makes me feel better about the rust on the transformers. I haven't decided yet if I want to open up the chasis or not. If I do, I'll certainly post pics. Thanks again.
 

smolder

Platinum Supporting Member
Messages
14,502
Rusty transformers aren't an indication of anything but time in the air with humidity. Don't try to remove the rust.

Everything looks fine. A well worn amp is a sign of lot's of use. The crappy sounding amps sit in used music stores and go home with bedroom players. I always think of the wear as a good indicator.

As for the speakers... DrBob is right. Seeing the front would confirm things. My guess is that those are not the original cones in the jbl's. First, I think those long white stickers come with OEM re-cone kits. The only place I've seen the is on reconed speakers. Also - many reconers will mark the backside with a china marker - typically initials, a date and maybe the shop that did the work.

If they are original, they will have white number stamped on the back of the paper reading 21032. That said... the early recone kits, even the K120 kits had that number. A single ripple in the surround is typical of original D cones... from the back it looks like yours are the double or w surround.

If you pull the chassis and pull off the dog house (squarish can on the tube side of the chassis... and post pics, you'll get plenty of insight here into the originality, mods, and potentially any obvious service needs.
 

FFTT

Member
Messages
28,354
The amp shows pretty obvious signs of damp location storage.

Hopefully a can of Deoxit will do wonders on all the cleanable components.
 

olin

Silver Supporting Member
Messages
627
Thanks all. Here are some shots inside the chasis (although I realize now one of them is blurry.)

One more coming from under the "dog house" as soon as I can get Photobucket to wake up.



 

smolder

Platinum Supporting Member
Messages
14,502
On the up side you have the blue molded caps intact that really helped the tone of blackface amps... and they are in the preamp. Those in the vibrato, reverb and power section are arguably less important. The pictures don't show the number, but you can probably improve the tone of the orange caps if they are labeled 715 and 716... though some guys love those.

I don't see a trem bug, so that section of the circuit may have been removed. Edit: scrathc that, it's fuzzy and under a big ceramic cap.

Some of the small value ceramic caps have been replaced with silver mica. I think they sound clear and clean... others think they sound strident.

I'd replace the orange/yellow paper cap in the bias section.

Someone here can help you date those blue Atom caps in the dog house. If they are over 10 years old you may want to replace them and not worry about it for the next decade.

The inside is dingy and rusty, but I don't know of that ever effecting tone. I've seen guys disassemble amps that look like this, buff out the chassis and reassemble... but that's way more work than I'd probably mess with.
 

Lance

Gold Supporting Member
Messages
10,871
Yes. I just got it yesterday and that's the way it was when I got it.
That's the first thing you should change out. You need to get four of the same type of 6L6 tubes that are closely matched, and sold as a set. That should solve a lot of the sound problems right there. Especially buzz, and hum.
 

El Jefe

Member
Messages
281
On the bright side, those filter caps look pretty fresh. The mismatched tubes might actually not be a problem as long as the two pairs are matched in terms of operating characteristics. Get them tested. And, even if it needs a new quad, those pairs might be usable in a smaller amp.

Those big gray resistors on the power tube sockets are also new. This thing has been serviced recently. Don't worry about rust, it means nothing other than cosmetics. Shouldn't take much to get it running perfectly.
 

olin

Silver Supporting Member
Messages
627
On the bright side, those filter caps look pretty fresh. The mismatched tubes might actually not be a problem as long as the two pairs are matched in terms of operating characteristics. Get them tested. And, even if it needs a new quad, those pairs might be usable in a smaller amp.

Those big gray resistors on the power tube sockets are also new. This thing has been serviced recently. Don't worry about rust, it means nothing other than cosmetics. Shouldn't take much to get it running perfectly.
Thanks! I'll probably hold off on buying tubes until I can get it into tech.
 

olin

Silver Supporting Member
Messages
627
Thought I'd bump this one more time in case the early morning crowd has any more insights before I make an appointment with a tech.

Thanks for all of your help guys.
 

theelectic

Member
Messages
298
If I'm reading the date codes right, the main filter caps (big blue ones) appear to be from 1998 and 2000. Might want to replace those (rule of thumb is 10 years), though the ones in my Twin are from 1998 and still work fine - no hum, ghost notes, or missing low end.

Looks like a few other mods/parts replacements in there, nothing major though.
 

Roe

Member
Messages
8,216
I'd replace the metal oxide 100k plate resistors with Allen bradley carbon comp resistors. And the orange drops with sozo blue molded. possibly also the 40uf screens filter cap with a 20 or 30uf one
 

Roe

Member
Messages
8,216
If I'm reading the date codes right, the main filter caps (big blue ones) appear to be from 1998 and 2000. Might want to replace those (rule of thumb is 10 years), though the ones in my Twin are from 1998 and still work fine - no hum, ghost notes, or missing low end.

Looks like a few other mods/parts replacements in there, nothing major though.
I've found the best sounding filter caps for twins to be TAD audio caps 220uf for mains and 20uf 550v for preamp
 

olin

Silver Supporting Member
Messages
627
Good stuff, thanks guys.

One thing I've noticed is that when it's cranked (yes, I can crank it at home, a sign of a problem, I'm sure), after I hit a bass note hard, it makes a "whump, whump, whump" noise, almost like helicopter rotors. Any idea what that might be??
 

smolder

Platinum Supporting Member
Messages
14,502
Good stuff, thanks guys.

One thing I've noticed is that when it's cranked (yes, I can crank it at home, a sign of a problem, I'm sure), after I hit a bass note hard, it makes a "whump, whump, whump" noise, almost like helicopter rotors. Any idea what that might be??
Not sure if you mean loud or dime'd... I've never been a fan of any blackface or silver face amps on 10. They just sound ragged to me.
 






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