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Post subject: Basket case or treasure? All original '67 Showman SF
Posted: Fri Feb 19, 2016 10:26 am
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Hi everyone.
I just recently pulled an amp out of storage that I haven’t played with in over 25 years due to a blown out power transformer. Back when the transformer blew I remember it making a huge mess. Filled the jam room with smoke and coated the chassis and components with a brown goopy film that eventually hardened and appears really difficult to clean off now.
Now that I have this amp in front of me I’m wondering what I should do with it. The main power transformer obviously needs to be replaced and I think the smaller T2 transformer let a little smoke out too. Other than that this thing is 100% original and un tampered with including original filter caps, tubes, two-pronged plug and “death cap”.

I’d like to start playing out of this amp again, I just don’t know if it’s worth the repairs or not. Can anyone tell me what it is I have in front of me? Is it rare? Collectors piece? Basket case? Good project amp?

Here’s what I know:
Serial # and transformer code put it at either ’67 or ‘68
Showman Silverface with drip edge
AB763 circuit
All original components including filter caps and two pronged plug
Original JBL D140F speaker in cabinet.

Can anyone please chime in and identify anything else I may have overlooked? And again, is it worth salvaging?

Here's a link to a bunch of photos I put on Dropbox.
https://www.dropbox.com/sh/63gy5rj70e4g4lv/AACqQBAaVMJSEafuSGgjHjcwa?dl=0

Thanks!
looking forward to thumping again


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Post subject: Re: Basket case or treasure? All original '67 Showman SF
Posted: Fri Feb 19, 2016 11:11 am
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oKors, welcome to the Forum! :)

Restoring this amp back to reliable use will depend on several factors.

1.) How much damage has been done to the tagboards and chassis. If the PCB that oozed out of the tranny soaked the circuit boards, you may need new ones. These would be very hard to find --- you may need to make your own. A word of caution here. PCB is hard on the skin and lungs and maybe carcinogenic. You'd need to use gloves, and be very careful cleaning the mess. I would avoid heating it.

2.) How good are you at repairing electronic circuitry.

3.) If you aren't going to do the repairs --- do know a good tech familiar with this era of Fender amps.

4.) Do you or tech have parts or are you going to need to buy all necessary items online.

5.) You need basic tools and a basic skill with a good DVM and solder iron.

6.) A work bench that you can rest the project for a good few months, while gathering parts and Googling what to do.


It maybe better to part out this amp and look for a nice silverface Showman Reverb. One that is working and may only need re-capping and new tubes.

Just a thought. Keep us informed.


Last edited by BMW2002Ti on Fri Feb 19, 2016 11:13 am, edited 1 time in total.

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Post subject: Re: Basket case or treasure? All original '67 Showman SF
Posted: Fri Feb 19, 2016 11:12 am
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Definitely a treasure!

I'd start by overhauling the power supply. Replacement trannies are available from a number of different sources or you could search for some original iron. Once you have the P/S squared away, power the amp up using a variac to determine the fitness for high voltage of the other components. Assuming the chassis passes the "smoke test", then it's time to check the tubes for serviceability. Replace as necessary (new power tubes should installed as a matched quartet). Set the bias somewhere between 33 mA and 39 mA according to the available plate voltage. This amp's output tranny is optimized for an 8Ω load.

The cabinet is a tone-ring model apparently configured for bass guitar (the D140F is a bass-specific speaker). If the driver requires a re-cone I recommend Orange County Speaker Service in LA or Dusty's Speaker Reconing in Connecticut.

Cosmetically, the furniture seems to be in fair shape and some general cleanup will improve the appearance. Use caution when working around the grill cloth -- that particular weave is no longer made. New control panels can periodically be found on Ebay but the silverface types are rare.

I've done dozens of these restorations and the efforts always pay handsome dividends.

Arjay

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Post subject: Re: Basket case or treasure? All original '67 Showman SF
Posted: Fri Feb 19, 2016 11:36 am
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Thanks for the reply guys!
I'd definitely like to NOT part it out if possible. Too much backstory and too significant of a piece of my history to break apart.

Retroverb... Do you think the cabinet is mis-matched to the head? or just had a different speaker put in? It looks as though someone pulled the insulation out at one point too. Honestly I never had the back panel off the cab until last night to take photos (smells like grama's attic in there). I don't think a re-cone is necessary. It looks fine and the front surround (suspension?) is still flexible. No way to know till it receives a signal.

I'd like to go the route of preserving this.
That being said, to answer a couple of BMW's questions; I'm an electronics grad now so I know my way around a DVM and soldering iron. I do know a guy who is an amp tech and these vintage amps are right in his wheelhouse and his favorite to work on. I will likely buy all my parts through him and have him guide me as to which components to replace and in what order.

For now, how would you recommend I go about cleaning this up? What can I use on the tolex and grill cloth? and for the metal/chrome bits... replace or will the rust buff out?

Thanks for the help!
I'll be sure to document my progress.


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Post subject: Re: Basket case or treasure? All original '67 Showman SF
Posted: Fri Feb 19, 2016 11:59 am
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If you feel comfortable and have the means --- restore this puppy. Parts can be found. Including OEM trannies. If you can't find the correct tranny, I recommend Hammond replacement.

You can construct a chassis cradle out of wood. To hold the chassis with the circuit facing you. And lift the irons the other parts off the working surface. A must in order to do good soldering.

First off... prolly redo the main power supply (PSU) caps and resistors. Replace irons that blew. Check the grid stopper and screen resistors on the 6L6GC output tubes. Be sure the bias supply circuit (including the pot) parts on in tolerance. Replace the cap(s) in the bias supply.

Go over all resistors and caps on the circuit board. Look for damage. You may want to lift one leg on resistors you suspect being damaged or out-of-tolerance. Measure their resistance. Buy a bunch (like 5) proper fuses.

Once all the parts seem to be in spec and damaged ones replaced, then get a set of tubes you know works, but you don't mind if they get damaged. Used are fine. Ramp up the amp with a Variac (as Arjay stated). Measure B+ voltages to be sure the PSU is ok. Make sure the output is connected to a dummy load or test speaker.

Measure voltages on tubes at other points noted on the schematic. Esp voltage points on PSU rail taps. And the tube's anode. Adjust bias.

If all goes well, you should be good to go, amp-wise. Put in tubes you want to use and re-bias.

I think this is the schematic for your amp. Believe me, after all is done, you will have memorized the schematic and layout. Prolly have dreams about them. :lol:

http://ampwares.com/schematics/showman_ab763.pdf

There are good reference sources for this type of restoration. Including online sources. I like Valve Wizard and Tone Lizard as starting points.

http://www.valvewizard.co.uk/

http://tone-lizard.com/contents/

Good luck! Keep us posted.


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Post subject: Re: Basket case or treasure? All original '67 Showman SF
Posted: Fri Feb 19, 2016 2:47 pm
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oKors wrote:
Retroverb... Do you think the cabinet is mis-matched to the head?


Possibly but I think not. The tone-ring Showman cab was discontinued in late spring of 1967 and only a handful with the drip-edge silverface cosmetics were shipped before production ceased. Likewise the Showman head (NOT the Dual Showman) was also retired about the same time.

As for the bass speaker, the D140F was a no-cost option that any dealer could order. The cabinet relies on the extra damping provided by the fiberglass pads for enhanced acoustic loading and I'd urge you to replace it as time (and money) permits. There are several Ebay vendors who sell complete kits.

Arjay

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"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


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Post subject: Re: Basket case or treasure? All original '67 Showman SF
Posted: Tue Feb 23, 2016 7:06 pm
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If you do decide to restore it, let us know how it turned out. We love seeing amps restored to their former glory!

T2

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Post subject: Re: Basket case or treasure? All original '67 Showman SF
Posted: Wed Feb 24, 2016 1:00 pm
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T2Stratman wrote:
If you do decide to restore it, let us know how it turned out. We love seeing amps restored to their former glory!

T2

Oh I will for sure. Looking forward to this as a new hobby/project!

Also one thing I never mentioned. 25 years ago I played bass through this... 25 years ago I was young, I didn't realize what I had at the time and I played through whatever I could (including my home stereo with tape deck queued on "record" so I could pass through the mic input :roll: )

Fast-forward to now and I should be lucky that there just happened to be a bass-specific speaker in that cabinet.
Long story short, if I'm able to resurrect this I'll pick up the bass again and use this amp to play through. Anyone here think this is a horrible idea? I don't know what the difference is in sound between an Showman and Bassman amp/circuit. I'm thinking it might sound kinda cool. Sounded awesome 25 years ago from what I remember. But that doesn't mean it was ever an ideal hardware combination. Hey, maybe that's why the PO pulled the insulation out of the cabinet... hmmm..

Cheers!


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Post subject: Re: Basket case or treasure? All original '67 Showman SF
Posted: Wed Feb 24, 2016 1:32 pm
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Sonically, the Showman and Bassman amps will share similar tonal characteristics. What gives the Showman the edge is more clean headroom (nearly twice the power in fact) and a superior speaker enclosure. My brother is currently playing a Dual Showman head through a Sunn 200S cab for small-to-medium club gigs and he finds it more than adequate for the task.

Arjay

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"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


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Post subject: Re: Basket case or treasure? All original '67 Showman SF
Posted: Wed Feb 24, 2016 11:21 pm
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Good bass = moving lots of air. I'm sure that Quad Reverb does that well. I know the Showman Reverb is killer --- coupled to a a full stack.

:lol:


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Post subject: Re: Basket case or treasure? All original '67 Showman SF
Posted: Thu Feb 25, 2016 11:08 am
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oK, I had to replace the PT in my '68 Dual Showman Reverb a few years back. The tech installed a new Hammond transformer, which I have been very happy with, actually prefer the sound now to the OEM part. Price for part (with the shop's markup, I'm sure) was about $90, tho' I've seen used Fender PT's on ebay for less.
Incidentally, the Showman used to be a very popular bass amp, and there are some who still use them for that.


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Post subject: Re: Basket case or treasure? All original '67 Showman SF
Posted: Thu Feb 25, 2016 11:43 am
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nyquilcoma wrote:
Incidentally, the Showman used to be a very popular bass amp, and there are some who still use them for that.


Indeed......

Image

Arjay

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Post subject: Re: Basket case or treasure? All original '67 Showman SF
Posted: Thu Feb 25, 2016 12:22 pm
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oKors wrote:
T2Stratman wrote:
If you do decide to restore it, let us know how it turned out. We love seeing amps restored to their former glory!

T2

Oh I will for sure. Looking forward to this as a new hobby/project!
Cheers!


My son and I have done a refurb of a Fender Amp each winter for the last four years...two Bantam Bass Amps, a '66 Bassman, and just this past winter a basket case '69 Super Reverb. When it turns cold here at the gateway to the west, it keeps us active and great father and son time. These last two amps he has done a good portion of the work.

T2

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Post subject: Re: Basket case or treasure? All original '67 Showman SF
Posted: Thu Feb 25, 2016 3:25 pm
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T2Stratman wrote:
My son and I have done a refurb of a Fender Amp each winter for the last four years...two Bantam Bass Amps, a '66 Bassman, and just this past winter a basket case '69 Super Reverb. When it turns cold here at the gateway to the west, it keeps us active and great father and son time. These last two amps he has done a good portion of the work.

T2


Cool legacy! Next winter, maybe a Deluxe Reverb? Or tweed Bassman? Pro? Maybe, a brownface or blonde?

:D


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Post subject: Re: Basket case or treasure? All original '67 Showman SF
Posted: Fri Feb 26, 2016 3:02 pm
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BMW2002Ti wrote:
T2Stratman wrote:
My son and I have done a refurb of a Fender Amp each winter for the last four years...two Bantam Bass Amps, a '66 Bassman, and just this past winter a basket case '69 Super Reverb. When it turns cold here at the gateway to the west, it keeps us active and great father and son time. These last two amps he has done a good portion of the work.

T2


Cool legacy! Next winter, maybe a Deluxe Reverb? Or tweed Bassman? Pro? Maybe, a brownface or blonde?

:D


Hmmm?....Sometimes this legacy has been dictated by what we can find to refurb. I am still convinced CBS dumped all their Bantam Bass Amps here in the St. Louis area, I have seen five or six here and never another one anywhere else!

We are really thinking of doing a Tweed Champ Kit this next winter. My son seems to think we're up to it, so why not?...the worst that can happen is I have to send it off to you or Retroverbial to make it work!

:lol:

T2

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