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Post subject: Tune-up costs for for an early 70's DSR?
Posted: Thu May 26, 2011 4:06 am
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Hi All,

I have the chance of buying a well-used, but fully functional, Dual Showman Reverb head for a good price ($475). Can you tech guys give me a ballpark idea what is a reasonable cost for a cap/filter/bias job? I already know that new tubes will be around $130. Just trying to decide if I am making a good investment versus going with a "newer" vintage amp that will most likely only need new tubes. Thanks!

Matt


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Post subject: Re: Tune-up costs for for an early 70's DSR?
Posted: Thu May 26, 2011 5:55 am
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mdortona wrote:
Hi All,

I have the chance of buying a well-used, but fully functional, Dual Showman Reverb head for a good price ($475). Can you tech guys give me a ballpark idea what is a reasonable cost for a cap/filter/bias job? I already know that new tubes will be around $130. Just trying to decide if I am making a good investment versus going with a "newer" vintage amp that will most likely only need new tubes. Thanks!

Matt

Not sure how much a tech will jack the prices of the caps up but if he uses F&Ts for the filter and bias caps and Spragues for the bypass caps the parts caost there should be around 50.00 give or take. For a good tech prob a couple hours worth of work. Dont know the hourly rate.
To see if its worth it....If the DSR is THE amp you want then its worth it.....


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Post subject: Re: Tune-up costs for for an early 70's DSR?
Posted: Thu May 26, 2011 6:55 am
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If the amp sounds good then you don't need the caps replaced. I may be extreme but in my opinion replace the filter caps only if you're getting 60hz hum with the volume down.

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Post subject: Re: Tune-up costs for for an early 70's DSR?
Posted: Thu May 26, 2011 7:11 am
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mhowell wrote:
If the amp sounds good then you don't need the caps replaced. I may be extreme but in my opinion replace the filter caps only if you're getting 60hz hum with the volume down.


Correction - that 120hz hum. 60hz is off the heaters. :?

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Post subject: Re: Tune-up costs for for an early 70's DSR?
Posted: Thu May 26, 2011 7:45 am
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mhowell wrote:
If the amp sounds good then you don't need the caps replaced. I may be extreme but in my opinion replace the filter caps only if you're getting 60hz hum with the volume down.

Or if you get "motorboating". :)


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Post subject: Re: Tune-up costs for for an early 70's DSR?
Posted: Thu May 26, 2011 8:38 am
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I do a visual of the power electrolytic caps. If you see pimples on the edges. Sign of leakage. Bulging in the center. Corrosion on either lead. I'd replace them with new caps---regardless of tone. It may sound great for 5-10 minutes. But, if the amp is pushed or you intend on using it everyday, more than 5 days a week... you risk further damage if too much AC is allowed through the supply, as the original caps are pushed beyond their limits.

Another really simple test, is take one of the main power filter caps out of the amp. Now feel its weight against a brand new cap of equal mfd and voltage rating. If the old cap's weight is much lighter than the new one... prolly most of the electrolytic fluids have leaked or evaporated from the original cap. Replacement time.

Always replace with as close new mfd caps as you can find. Higher voltage rating is better, as long as it'll fit in the chassis.

Good luck with that amp!


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Post subject: Re: Tune-up costs for for an early 70's DSR?
Posted: Thu May 26, 2011 8:47 am
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What's "motorboating" Arjay??? Thanks for the advice guys!


Matt


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Post subject: Re: Tune-up costs for for an early 70's DSR?
Posted: Thu May 26, 2011 9:42 am
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"Motorboating" is a phemonenon that occurs with microphonic components -- usually, but not always, signal-chain caps. The sound is reminescent of a 9HP Evinrude trolling motor and it will occur spontaneously, regardless of whether an input signal is present or not. Isolating and identifying such defective components is usually a time-consuming PITFA.

You've heard various opinions about the need for new filter, biasing, and bypass caps -- I shall leave you with this: Replacing these caps is like insurance. Better to have them and not need them than to need them and not have them. If one or more of the filter caps fails, it likely will be catastrophic, with the distinct possibility of dragging down the entire power supply. Priced a Showman power tranny lately? They're over a C-note now. Where's the sense in deferring a fifty-dollar outlay only to put a $100 tranny at risk?

'Nuff said.

Arjay

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Post subject: Re: Tune-up costs for for an early 70's DSR?
Posted: Thu May 26, 2011 9:46 am
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Amen to that! Sounds like money well spent. 8)

Matt


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Post subject: Re: Tune-up costs for for an early 70's DSR?
Posted: Thu May 26, 2011 10:36 am
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Barring any unforeseen discoveries once I open up the chassis, these four-bottle Fenders generally run around $250 to get them reliably road-ready.

That's a full set (usually) of new tubes, new filter and bias caps, new screen resistors for the power-tube sockets, and a can of De-Oxit to clean the pots, switches, and jacks.

Arjay

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Post subject: Re: Tune-up costs for for an early 70's DSR?
Posted: Thu May 26, 2011 11:35 am
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Rebelsoul wrote:
mhowell wrote:
If the amp sounds good then you don't need the caps replaced. I may be extreme but in my opinion replace the filter caps only if you're getting 60hz hum with the volume down.

Or if you get "motorboating". :)


That could be but I don't even know what motorboating is. Sorry. :D

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Post subject: Re: Tune-up costs for for an early 70's DSR?
Posted: Thu May 26, 2011 5:46 pm
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Arjay explained it pretty well,it happened to my '66 Deluxe Reverb,I was jamming with some guys in Huntsville,AL.,and all of a sudden the amp started making a sound like a fast,bbbrrrrrrrrrrrr....with the speaker looking like it was going to jump out of the cabinet.
I shut her down quickly,and the bass player told me what he thought the problem was....one thing about vintage amps,they require upkeep and replacing of faulty parts for the good of the amp,anybody not willing to do that will damage expensive parts because of faulty cheaper ones not replaced because somebody wants it to remain "mint".


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Post subject: Re: Tune-up costs for for an early 70's DSR?
Posted: Thu May 26, 2011 9:41 pm
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+1, Reb

I had a '67 Bassman that gave me fits for two weeks as I replaced component after component trying to isolate the cause. It turned out to be the tone cap on the bass instrument channel's "deep switch".

Arjay

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