First, Hello to everyone. Its my first post. I have a couple of SS amps, My Tech 21 TM-60, an older Yamaha G-112, An even older Peavey Renown 2-12, a previous and deceased and missed, GK-SEL-2100 (RIP, sniff)
Somehow I've wound up with my sons RB400, which I took out to a BBQ/jam over the weekend. I set up and powered on but there was no sound. Pilot light lit, speaker plugged in, (swapped cable JIC), but no sound.
As I inspected the head for any obvious problems, the top of the amp was very warm (not hot) to the touch, even after only a short time. The heat sink was also fairly warm but not hot, considering the under 2 minute run time.
I traced back the amp usage over the last 3 months and I took it out one other time to power a floor monitor. The monitor didn't work and I blamed it on the sound guy or the send cable. I'll bet the amp was failing then also.
Yesterday I got to ask my son if he'd had any problem and he didn't recall, BUT, (big BUTT), there might have been one time last year he was running some music through the amp for a party and there were "Sprinkles" and he covered the amp with a plastic tarp. Possible red flag there I think.
What might be the initial trouble shooting points on this amp? Output transistors, power supply, (amp lights up). Is there a fuse on the output?
I'm going to rummage up an schematic and get prepared in the mean time.
I've got above beginner skills, not expert. I've built a 2-6L6 tube amp from scratch, (no kit, sourced parts), but the well of knowledge is quite deep and I'm just dipping a ladle in.
Thanks for any and all info,
Dez
NYC
Hot but mute amp usually means shorted speaker cable.
*So far* the amp is not dead, and if you quickly understand what's happening and turn it off, usually no big harm is done.
Otherwise.....
Start by building a lamp bulb limiter and googling the schematic.
Asking for it at GK usually brings back some .pdf too.
Post it here.
Hi Dez, welcome.
For people with "tooob" experience who aren't too sure of transistors, I've written a page here (http://www.ozvalveamps.org/repairs/solidstateamprepair.htm) on S.S. amp repair.
Very nice page Roly. I've sent off an email to G-K. I have a bulb limiter from firing up my recent amp project.
Dez
I've gotten a response from G-K sales and IT coordinator requesting a serial number which I sent back already. I think I'll see some .pdf's from this. I'll host them as needed.
Meanwhile, I took a spray can of cleaner/lubricant and hit all the inputs and outputs, the send and return as well. Bam !! She's back online.
So I'm going to call it a little moisture and unuse, plus storage in a basement area, creating light to moderate corrosion on any or all of the jacks.
Its been idling for 20 minutes and the top is cool to the touch.
Beer is in order.
Gary
I will post the schematic as soon as it arrives.
Posted:
http://www.ssguitar.com/index.php?topic=3028.0 (http://www.ssguitar.com/index.php?topic=3028.0)
Do not use lubricant on electrical contacts!
A lubricant is a film of some hydrocarbon, silicone or fluorocarbon.
What do these materials have in common? They don't conduct!!!
When you put a lubricant film between metal contacts, you're creating a capacitor. If the contact was so dirty that it didn't work, the lubricant may improve it, but the result won't be ideal.
The best contact is made by smoothly polished metal surfaces that are free of any dirt, film or oxidation. The smooth polishing maximizes the contact patch area, and freedom from nonconductive material and oxidation ensures that the contact points have near zero resistance, and are ohmic (distortion free).
Use metal polishing paste on a cotton swab to polish the contacts inside the jack: only a small quantity worked into the swab, so as not to leave a build-up in there. Follow up with a clean cotton swab loaded with rubbing alcohol to remove the paste, and give it a final rub with a dry swab.
(I use toothpaste, with great results. When I run my tongue over the jack contacts, they have that fresh-from-the-dentist feeling, and none of my gear has ever had a cavity!)
QuoteDo not use lubricant on electrical contacts!
???
QuoteA lubricant is a film of some hydrocarbon, silicone or fluorocarbon.
What do these materials have in common? They don't conduct!!!
That's *exactly* the point, we don't want randomly conducting stuff there.
QuoteWhen you put a lubricant film between metal contacts, you're creating a capacitor.
If and only if they do not touch each other .... which is not the case. ::)
QuoteIf the contact was so dirty that it didn't work, the lubricant may improve it, but the result won't be ideal.
The lubricant plus the light solvent plus other additives present wet and soften big way whatever grime is present, so it's much easier to clean.
QuoteThe best contact is made by smoothly polished metal surfaces that are free of any dirt, film or oxidation. The smooth polishing maximizes the contact patch area, and freedom from nonconductive material and oxidation ensures that the contact points have near zero resistance, and are ohmic (distortion free).
Nice.
The contact cleaner does the chemical part of that job.
QuoteUse metal polishing paste on a cotton swab to polish the contacts inside the jack: only a small quantity worked into the swab, so as not to leave a build-up in there.
Nice, but often impossible to do.
If you spread typical leaf contacts so much so as to have space for a cotton swab, they'll probably never make good contact again, if any.
QuoteFollow up with a clean cotton swab loaded with rubbing alcohol to remove the paste, and give it a final rub with a dry swab.
See above.
Quote(I use toothpaste, with great results. When I run my tongue over the jack contacts, they have that fresh-from-the-dentist feeling, and none of my gear has ever had a cavity!)
You must be joking.
Lube in a pot or fader is not meant to get between the contact surfaces. It is assumed they touch. The lube is there to assist smooth movement, and to also loosen any goo that might get in the works.
Think of a car engine, covered in a thick grime. hard to wipe off with a finger. Now douse an area of said engine with fresh oil, and smear it around. It loosens the old thick goo, and you can now easily wipe an area clear with a fingertip. In a pot nice fresh lube allows the little wiper feelers to slide along easily pushing aside any bits of debris.
"Lubricating contact cleaner" was always a staple in electronic service. Try squirting plain old Deoxit into a 60mm fader on a mixer. It now may have good electrical contact, but the sliding motion is sticky. Now squirt in some Caig faderlube, and it smooths right out.
I understand the point on lube creating a coating. I was taken by the "Cleaner" part of the label. Since the condition has been remedied, and the amp will get some use and stored in a nicer environment, I could shoot a blast of electrical cleaner, not a lot, but perhaps to clear off and residuals.
I was going to buy some Deoxit online and the supplier couldn't tell me which of his products would be best suited for my needs, I lieu of his customer service, I went to radio shack to get abused and spend too much but I had something in my hands immediately
I have a very long distance suspicion of cans of "instant technician", particularly when there are dozens of different formulations.
"I gave it a spray of CRC"
"Which one?"
I had a long running nightmare saga with a radio station where people would treat every problem by giving it a spray of CRC. The stuff they actually had was a moisture dispersant and contained a light fraction that caused every cap in the desks to swell up, and a light oil that was literally running around the base of the desks.
- silicon sprays, etc, are an absolute no-no around electrical contacts.
- dry alcohols such as isopropyl (tape head cleaner), methylated spirit, (or Russian vodka 8) ), all make good contact cleaners.
- the edge of a newspaper makes an excellent mechanical contact scrubber; rough enough to clean, not rough enough (or thick enough) to damage.
The "medicinal ingredient" in Deoxit is oleic acid: a fatty acid found in vegetable oils such as olive oil.
The same stuff is also used in some traditional metal polishes. I think Brasso contains it, or may at one point have.
It cuts through oxidation, perhaps not so differently from the action of solder flux.
I've read some claims by hobbyists that you can make your own homebrew Deoxit equivalent by cutting some oleic acid in a petroleum distillate: camp stove fuel like Coleman or lighter fluid. I haven't tried it myself, yet, but it sounds promising.
The brand name DeOxit is priced like it's some of elixir of immortality made from the extract of the flower of a rare herb that only thrives in one single tiny forest somewhere in Nepal, and blooms only for one week, once every 23 years.
See here: http://www.dialcover.com/components.html
Scroll down to "CEASE & DESIST" CONTACT CLEANER
xP
You can pay twice the real price by getting it at Radio Shack. Or you can pay $7-8 a can by getting Deoxit from a regular supplier. I run a commercial repair shop, and one can lasts me a very long time.
One can make some sort of ersatz Deoxit in the bathtub, but getting it into the aerosol can is trickier. I can direct my spray up into a pot. Much harder using an eye dropper. And to say Deoxit is jus a can of oil is like saying a prime rib dinner is just a slice of cow.
Quote from: Roly on July 10, 2013, 09:55:43 AM
I have a very long distance suspicion of cans of "instant technician", particularly when there are dozens of different formulations.
"I gave it a spray of CRC"
"Which one?"
I had a long running nightmare saga with a radio station where people would treat every problem by giving it a spray of CRC. The stuff they actually had was a moisture dispersant and contained a light fraction that caused every cap in the desks to swell up, and a light oil that was literally running around the base of the desks.
- silicon sprays, etc, are an absolute no-no around electrical contacts.
- dry alcohols such as isopropyl (tape head cleaner), methylated spirit, (or Russian vodka 8) ), all make good contact cleaners.
- the edge of a newspaper makes an excellent mechanical contact scrubber; rough enough to clean, not rough enough (or thick enough) to damage.
And I suppose the bottle of Vodka is head cleaner? Yeah right,, Which head,, the one on the bench or the one on your shoulders. :lmao:
Phil.
Quote from: Kaz KylhekuThe brand name DeOxit is priced like it's some of elixir of immortality made from the extract of the flower of a rare herb that only thrives in one single tiny forest somewhere in Nepal, and blooms only for one week, once every 23 years.
...gathered by comely virgins on the full moon (who make $1000/m speaker cable on their days off).
Thanks for the clue about oleic acid.
Quote from: EnzoYou can pay twice the real price by getting it at Radio Shack.
Also known here as
Tandy, "utterly clueless", and several much less flattering names. Bought out by
Dick Smith Electronics, itself having been bought by supermarket chain
Woolworths, now the whole lot flogged off "for a bargain price of $20 million" to some investment company
Anchorage Capital Partners and about as far removed from its roots as a component supplier as one could get; the whole mess now Zombiefied walking dead. May they all rot in hell.
Quote from: Enzobut getting it into the aerosol can is trickier.
Artists have a neat little mouth-powered gizmo called an air brush, and I use drinking straws like a pipette ('course with Vodka you can suck as well as blow, to good effect).
I wouldn't have had (as big) a problem if the radio station had been using DeOxit, or in fact anything that was actually a contact cleaner, but the particular CRC they were wedded to was a moisture dispersant for drying out electrical stuff like tractor wiring and contained a high viscosity oil as well as light fractions.
I had a Paddy Roberts LP one time which advised that "This record should be cleaned with a very dry martini". MP3's are nearly as much fun.
Quote from: Roly on July 11, 2013, 03:39:06 AM
Quote from: Kaz KylhekuThe brand name DeOxit is priced like it's some of elixir of immortality made from the extract of the flower of a rare herb that only thrives in one single tiny forest somewhere in Nepal, and blooms only for one week, once every 23 years.
...gathered by comely virgins on the full moon (who make $1000/m speaker cable on their days off).
Thanks for the clue about oleic acid.
But, wouldn't you know it, oleic acid is also priced wildly, like the milk squeezed from the teats of Buddha.
Some medical grade of it ready for use with bacterial cultures and can set you back a hundred bucks for a measly 25 ml!
Some other grades are more reasonably priced, like 25-30 bucks a liter.
Check the lab chemical suppliers "Sigma-Aldrich" and "VWR". I contacted the chemistry department at my old alma mater, UBC, and they tipped me off to these.
FWIW I checked my Industrial supplier price list.
Oleic acid is *cheap: less than U$5 a liter.
Only drawback is he sells it by the 200 liter drum (55 Ga. drum)
But I'll ask at a smaller chemical retailer shop.
Even if he charges U$10 or 15 a liter, it's cheap.
This is all well and good, and that stuff may be the majority ingredient, but it isn't the only ingredient, so this isn;t one of the cases where, "all you have to do..."
Next up, I'm saving animal fat from my cookstove and ash from my fire. Tomorrow we'll have SOAP!!
Agree that it must not be the only ingredient, and even worse, it *must* have some nasty chemical (in very small amounts) which is very important.
FWIW I make soldering flux (mainly to spray my just etched PCBs) out of pine rosin and alcohol or toluene (depending on how fast I want it to evaporate and what buzz I want to get today :( ) but I know that an ingredient which "accelerates" soldering and lets it attack much dirtier copper is one form of **mercuric chloride** (or bichloride).
Poisonous as H*ll :loco
No way I'm touching or breathing that .
Ok, Multicore solder already has it ... but I'm not adding any on my own will, so .....
Additives "improve" products but many times they are *very* nasty.
http://www.nlm.nih.gov/medlineplus/ency/article/002474.htm
Quote from: J M Fahey on July 09, 2013, 09:17:45 PM
QuoteDo not use lubricant on electrical contacts!
???
QuoteA lubricant is a film of some hydrocarbon, silicone or fluorocarbon.
What do these materials have in common? They don't conduct!!!
That's *exactly* the point, we don't want randomly conducting stuff there.
QuoteWhen you put a lubricant film between metal contacts, you're creating a capacitor.
If and only if they do not touch each other .... which is not the case. ::)
Okay, J.M. has set my head straight about this.
After some weeks of experimenting, I'm a convert: lubricant is good, at least in sliding contacts.
Hypothesis: the coating provides an oxygen barrier, inhibiting oxidation, and when you insert the plug into the jack, it wipes off, allowing for the metal surfaces to cut through and make contact.
I have used this product to clean all the jacks and plugs in my rack. Guitar to rack, between the rack units, and power amp to speaker:
http://www.kleenflo.com/en/productpages/4168.htm
I use this light machine oil on bicycle chains and all small lubrication tasks that don't call for something specific.
The audio results are fantastic. Smooth, silky, well-articulated sound. I just did a re-application because I was hearing something "off", some harsh brittleness in the tone. It was instantly gone. The bass response is excellent, which dispels the hypothesis that the film creates poor contact combined with capacitance that lets through higher frequencies. Obviously there is good DC contact.
So, to heck with boutique contact cleaner: a $6, half-liter bottle of oil does the job.
This particular stuff is great: according to the MSDS it has hydro-treated as well as napthenic oil, a petroleum solvent to help it penetrate (smells like fuel or naptha), as well as zinc alkyldithiophosphates: anti-wear, anti-corrosion additives.
Someone has studied the latter in connection with electrical connections. I'd love to get my hands on the full text of this paper: http://link.springer.com/article/10.1023%2FA%3A1019175509680 "Electrical contact resistance studies on zinc dithiophosphates".
Now I wouldn't go as far as using oil on non-sliding contacts, because of the lack of a wiping action to cut through the film. Oil inside a relay? Forget it! The best thing for non-sliding contacts is to be oxidation-free, enclosed in an air-tight container that is filled with an inert gas. E.g. magnetic reed switches are that way.
QuoteHypothesis: the coating provides an oxygen barrier, inhibiting oxidation, and when you insert the plug into the jack, it wipes off, allowing for the metal surfaces to cut through and make contact.
Yes, that's the point.
Besides oxygen, air contains corrosive gases , sulphur dioxide among others (a byproduct of burning fuels) which together with ambient humidity makes sulphuric acid, and other nasty products.
Exposed copper/brass/silver/tin get a thin but murky film which both disturbs plain contact and solderability.
FWIW a few years ago some 7.65mm Argentine Mauser rifles were sold.
Made in Germany in 1895!!!! they had rested unused covered in thick protective grease , wrapped in waxed paper, resting inside mold and moth eaten humid wooden crates.
They were in *PERFECT* condition, like fresh out from the Berlin factory !!!
One of the metallurgical shop maxims: "Grease is the Machine's Friend!!!!"
Just a little point that many relay contacts are constructed so that they do wipe, but something to seriously avoid are things that contain silicon compounds as this has immense surface tension and can migrate along metres of cable and form insulating silicon oxides on contacts.
Do you have much of a problem with Mause's over there JM? We don't have them here. Mice, Drop Bears, sundry snakes and spiders, but no Mause's thank goodness. {Don't tell me, let me guess, they sell them alongside the pickled Armadildos, right?}
I got some syringes from a drug store and now I'm injecting oil into pots. Very good results.
I measured a slightly lower wiper resistance in one test unit. It went from 1.5 ohms to 1.0.
The one in my guitar is absolutely silent at high gain, and feels almost strangely smooth, like you're turning a hot glass rod stuck into paraffin wax or something.
Little by little I will work my way through all the pots, including the 31 sliders on the graphic.
Just compare the top 4 elegant Argentine Mause(r)s to the chunky rough British Lee Enfield at bottom.
Included just because beauty is always relative to something else :lmao:
(http://media.liveauctiongroup.net/i/11425/11704965_1.jpg)