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Post subject: A Mystery?
Posted: Tue Feb 17, 2015 1:35 pm
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Before I realized all of the earlier "Twin Reverb Won't Power Up" threads were redundant, asked and answered questions, I had kind of a similar experience I wanted to ask you vintage Fender gurus about. As we all know, 40-50+ year old amps may have their peccadilloes...
So yesterday I go to crank up my '68 DSR, and sit down to a solo session. I hadn't had the amp powered up for a few days. Last time I used it, it performed just as fine as always. I turn it on to standby setting, and give it a few minutes to heat up, cricket light comes on. After a few minutes I flip the standby to play mode and...nothing. No sound, nada.
I freak, the dollar sign pouring out of my eyes. I turn the amp around and see no glow from the power tubes. I quickly turn off and unplug the amp.
I take off the back panel and start checking stuff. The fuse looks fine. I wiggle out each power tube-each looks OK, no signs of scorching, flashing, burnt or fused filaments, etc. I firmly re-seat each power tube. I pull the covers off of each pre-amp tube-again, everything looks kosher. I firmly re-seat each pre-amp tube. All tubes are only about two years old, and have had limited wear. I check the speaker cable from the speaker out on the amp to the jack plate on the cabinet-cable housing is a little loose at the cab end, but I screw it up tightly. I check the connections on the reverb/trem and the foot switch-unlikely but you never know... I put everything back where it should be, plug the amp back in, turn it on, and voila! The DSR is working as well as it ever has!
Any ideas as to what this could be about? Or is it just another case of the ancient amp gremlins?

On a wholly unrelated note, do you think this local C/L item might be worth checking out if I could pick it up for $400?
https://baltimore.craigslist.org/msg/4879388751.html


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Post subject: Re: A Mystery?
Posted: Tue Feb 17, 2015 1:42 pm
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Are you certain that your instrument cable was fully seated in an input jack?

If so, disregard.

You might try spraying the on/off and standby switches with De-Oxit. Give them each a good squirt then cycle them briskly several times.

As for the SR listed on C/L, yeah......four bills would be about right. It'll need a complete, new cabinet plus whatever electronic TLC is required to bring it up to factory performance, reliability, and safety specs.

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: A Mystery?
Posted: Tue Feb 17, 2015 4:38 pm
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Thanks, Arjay.
Yeah, I checked and re-checked all the input jacks with different cables firmly, connections were solid.
I don't understand how that could have affected the power or pre-amp tubes not firing up, tho'. Is it possible that a loose, or improperly seated tube somewhere in the chain could have prevented power from flowing through the circuit? Like I said, none of the tubes lit up, and were even cool to the touch when I removed/re-seated them.
I do have a dry, dusty house tho' and a blast of contact cleaner for all pots and switches is probably about due.
I think I am gonna go check out the SR from the C/L ad, and see what's up with it. The cab is definitely a beater, and it looks like a couple of the speaks are probably not original. Any off the top of your head common causes for the non-working tremolo in a Silver face Super?
I regularly see Silverface Fenders listed locally in the $400/$500/$600 range for Twins, Supers, various Bassman configurations, etc. I know the larger amps are out of favor these days, but for real PTP wiring, tank-like durability, iron and tone you can't get these days (or only get in "boutique" amps costing thousands of dollars more), I wonder if the market will ever come around to recognizing there are still bargains to be had?
Not everybody has the bucks for Blackface Deluxes, Princetons and Pro's, and the supply is dwindling anyway. Hell, even Silverface Broncos and VibroChamps can fetch upwards of five bills these days.
Will the big Silverfaces ever get the respect they deserve?
Sorry about the rant. Time to get off of my soapbox. Thanks for letting me vent. O...


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Post subject: Re: A Mystery?
Posted: Tue Feb 17, 2015 4:46 pm
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The trem issue is likely a dead tube or a bad opto-isolator. A few bucks to fix if you doing it yourself. If not, take it to a trusted amp tech and have him refurbish anything that looks wonky. Filter, bypass, and bias-supply caps (all of them electrolytics) would be a good starting point for a proper overhaul.

Arjay

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Post subject: Re: A Mystery?
Posted: Tue Feb 17, 2015 8:29 pm
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nyquilcoma, HI there!

I recommend getting some CAIG Deoxit GN-5 and applying a light amount to the pins and sockets of all tubes. Reseat each tube a few times to get rid of any surface patina which maybe causing a temporary contact issue.

Same treatment for jacks, plugs, power lamp and its holder. Switches and pots. I use CAIG Fader Lube on the pots, to help protect the carbonize contact surfaces and onboard lube within the pot.


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Post subject: Re: A Mystery?
Posted: Tue Feb 17, 2015 11:04 pm
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As always, thank you for your replies, gentlemen. I'm off to get a fresh can of de-oxit tomorrow, and will give all contact points a squirt.


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Post subject: Re: A Mystery?
Posted: Wed Feb 18, 2015 3:23 am
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If you use a cleaner in a switch, you can do more harm than good by flushing out the lubricant. Then you risk turning a good switch into a bad one. :idea:

In fact, I have never found the need for any kind of cleaner on any amp components except the pots, ever. How some guys seem to fix nearly every amp problem with De-oxit is amazing to me. If the switch is going out, replace it instead of forestalling the replacement by hosing it down. The standby switch has nothing to do with the tube heaters anyway, they aren't fed from the DC circuit, so why mess with something that can't possibly be the problem?

BTW, does "DSR" stand for a Deluxe Silverface Reverb?

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Post subject: Re: A Mystery?
Posted: Wed Feb 18, 2015 7:11 am
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Shimmy, that's why I recommend CAIG Fader Lube for pots. Anything that has onboard lube and/or carbonized contacts. No problems, so far.

These older amps often have issues with contact surfaces. Due to surface rust. I've never had a problem using a good contact cleaner. Key is to use SMALL amounts and wipe off excess. Anyhow, that's my experience.

http://store.caig.com/s.nl/sc.2/category.293/.f

I believe that DSR = Dual Showman Reverb


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Post subject: Re: A Mystery?
Posted: Wed Feb 18, 2015 9:08 am
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shimmilou wrote:
BTW, does "DSR" stand for a Deluxe Silverface Reverb?


Dual Showman Reverb

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: A Mystery?
Posted: Wed Feb 18, 2015 1:51 pm
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Ah! Thanks Retroverbial/BMW2002Ti. I just wanted to be sure that the tubes' heaters weren't fed from the DC, and thus the standby switch would have nothing to do with the tubes not glowing, nor would a socket's tube pin connection cause all tubes' heaters not to glow. So, hosing the amp's components down with cleaner would be useless.

More than likely, there is a poor connection at the heater source voltage, maybe a bad solder joint at the beginning of the heater circuit (first tube socket connection?). :idea:

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Post subject: Re: A Mystery?
Posted: Wed Feb 18, 2015 2:22 pm
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shimmilou wrote:
More than likely, there is a poor connection at the heater source voltage, maybe a bad solder joint at the beginning of the heater circuit (first tube socket connection?). :idea:


+1

I would check that as well. A continuity check between the pilot lamp and the heater pins at the V10 socket may be revealing. If there's an intermittent connection there, the pilot lamp would light but likely none of the tubes would. And as we all know, no heaters = no mojo.

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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