Roll your own multisection caps?

[RutherfordBrave]

I've always been one for keeping amps the same as they came, but yesterday I acquired a 1965/6 Guild Thunderbird (v1) for dirt cheap. It has been somewhat aesthetically molested, but everything is bone stock in terms of electronics as far as I can tell. Besides the background hum and other signs of needing filter caps, it sounds pretty great. Because of the cosmetics of the amp, I'm leaning towards keeping this project as inexpensive as possible. Problems with this:

1) I can't find a schematic for the amp.
2) There are clearly two multisection caps at 40/40/40/40 375V. Two of the others are paper, and the writing has faded completely over the years. See #1.

I figure this is the place to get examples of converting from cap cans to individual caps -- can anyone give me advice, or at least a schematic for how this is done? This is new territory for me.

[Steve Conner]

A multisection cap is just a bunch of individual caps with their negative terminals connected together. So a 40/40/40/40 should have 5 terminals.

Pretty trivial to replace with four individual electrolytics once you've figured out which one is the common negative (hint: it's usually connected to ground)

[g1]

To keep it looking stock, some here have gutted the cap cans and inserted modern single caps, in your case this would involve stuffing four 40uf's in the can. A bit of searching on the forum should find you some examples.

[RutherfordBrave]

Well that seems pretty trivial then. Any advice on where to get a schematic?...

[tedmich]

is it a Thunderbird Superstar?

Prowess Amplifiers - Misc - Schematics - Thunderbird Superstar - Trem Reverb twin 6L6s power supply

Prowess Amplifiers - Misc - Schematics - Guild Thunderbird and Superbird - Power supply PI Output Tubes

I personally wouldn't pot up ELs in a can, as they can overheat and need to vent. I'd maybe tack them to the sides with hot melt or epoxy

[RutherfordBrave]

There was an earlier version of these things (ie. the one I have) before those schematics. Not sure what they do/don't have in common, but there are some obvious differences just in the chassis layout. The one I have mounts the reverb in the chassis itself rather than in a separate pan, and the Thunderbird v2/Superbird have a breakout unit or something.

[tedmich]

really old and/or obscure amps can have very rare (if any) documentation, but on the bright side they are sometimes quite easy to figure out! Some amps (VHT!) never have schematics!

[RutherfordBrave]

This site appears to have one for sale for $15, but who pays for things anymore?! Pretty surprised it's not anywhere on the interwebs...

[hasserl]

Re the schematic, trace it out yourself. There is no better way to familiarize yourself with the design, layout and construction of the amp than to trace out the schematic. Not too hard to do and takes maybe an hour of your time, depending on how tightly packed it all is and how hard it is to follow all the wires to their destinations.

[RutherfordBrave]

One of the great "features" of this amp appears to be separate PCBs for different parts of the circuit. Those PCBs are mounted with the components facing the top of the chassis, and as such have to be removed in order to work on things... I agree though -- probably my best option is just to roll up my sleeves and do it myself. I'll have to do it anyway to replace some of the multisection caps.

[johnk_10]

if it were me, for the 40/40/40/40@375V, i'd probably replace it with a 40/40/40@525V (this one: More Info for item C-EC40X3-525) and then use a single 40 sprague atom for the forth one.
your's shuld have 4 terminals, plus the four lugs on the case which is the ground.

[hasserl]

Vibroworld used to have 40/40/40/40 caps available, but they've been down for several years, with the same message showing on the main page that they will be back up soon. Weber VST will custom build multi-cap cans to suit your needs, but last time I inquired about a 40/40/40/40 they said they couldn't do that because the physical size of the individual caps wouldn't fit inside the cans they had.

[RutherfordBrave]

My original question was really one of economics vs. originality. A cap can runs $30-40, where as the caps themselves can be purchased for as little as $1.85 ea (from Weber). Brings the cost down under $20 vs. $70. This amp is in pretty rough shape and I picked it up for a song -- I'm looking more for function over form as a result. Can anyone give me reasons not to use Weber electrolytics?

[Steve Conner]

Just the cost of your time in figuring out a way to mount the new electrolytics. For a tech who charged $40/hour, that might be a reason to use the can. For a DIY repair, it's not.

[Enzo]

I rarely buy multicans, only if ther is a space problem.

Caps today are lots smaller than the same cap of old. A four section can puts all teh caps in the same place and you trail wires around the amp. Individual caps can be anywhere, not necessarily in the same spot. I sometimes even mount a terminakl stip in a chassis to make convenient tie points for individual caps.