AAAUUGGHHH!!!

[pollyshero]

I recently got a good deal on a Crate (never mind...) Blue Voodoo 6212. Previous owner said it crackled & sputtered & made horrendous noises - so I got it for less than $100.

I have been unable to duplicate the problems he was having - Thing worked like a charm for months & my neighbors are very glad I'll be moving next month.

Anyway... The amp came to me with 6L6's. If you're familiar with the Blue Voodo, it will also accept EL34's (boasting some "voodoo"-like self biasing circuit. I wanted to give it a shot so I got some EL34's & plugged 'em in. Owner's manual says to let the amp idle (off stand-by) for at least 20 minutes before playing (one supposes to give the voodoo a chance to do it's thing).

20 minutes later? Nothing. Tubes aren't lit. Not even warm. All pilots are lit, preamp tubes are lit, channel switching works & the pretty LED's light up. No sound whatsoever.

I figured I got ripped on the tubes (but the guy said they were brand new!). So I put the 6L6's back in, and...

So. I'll take a little ribbing for buying the Crate (but not much), but once past that - any thoughts or words of encouragement before I rip 'er apart? I'd really like to get it going again 'cause it wasn't a bad sounding rig - very nice for blues & classic rock.

Original intention was to check/repair the circuit board, replace any switching that needed it & re-flow all the solder joints. Aside from checking the sockets & connections to them, any other advice? The problem appears to be isolated to the output tubes.

[UnklMickey]

AAAUUGGHHH!!! indeed!

i just made a long reply to your thread and lost everything before i posted it.

long story short:

let this one sit 'til after the move. concentrate on getting all your "stuff" in one pile.

make sure to take a fire extinguisher or ten with you.

maybe the filaments are actually lit, but it just seems like they aren't 'cause the room isn't totally dark.

you can pull all the power tubes and (with the power off) measure resistance between pins 2 and 7 of any (power tube) socket should see a fairly low resistance across the filament winding of the power transformer. very high or infinite resistance? start looking for where you lost continuity in the filament wiring.

if you measure the AC voltage between pins 2 and 7 with the power on, BE CAREFUL. there are LETHAL voltages on pin 3 (plate) and pin 4 (screen grid) of those tubes.

good luck, and keep me posted when you get started.


unk

[pollyshero]

Good advice on all fronts - thanks.

And to anyone else reading, unk's admonishment to BE CAREFUL is not undue concern - Heaven has it's share of even experienced, careful amp techs. Even if "Safety" isn't your middle name, ANSWER TO IT.

[UnklMickey]

UD,

i was over at schematicheaven and they have a set of schema for the 60w blue voodoo.

so whenever you get to where you're ready to open it up, go here:
www.schematicheaven.com/newamps/crate_bluevoodoo_60w.pdf


the board for the 6L6s is separate, so the problem is likely in the connector.
BTW the 6L6s take 0.9A of filament current. the EL84s take 1.5A.

probably the contact was marginal before you made the swap.

the extra load of the EL84s was the nail in the coffin.



unk

[pollyshero]

Unk,

Thanks for the tip! I have the schems from St. Louis Sound already but haven't had much chance (or reason) to peruse them. All my stuff's still in storage... (still sleeping on the buddy's couch).

But I certainly appreciate you taking a look. I'll let you know how it turns out.

THANKS!

[sumgai]

PollysHero says:

I wanted to give it a shot so I got some EL34's & plugged 'em in.

unklmickey says:

BTW the 6L6s take 0.9A of filament current. the EL84s take 1.5A.
....
the extra load of the EL84s was the nail in the coffin.

Whatsa matter, unk, you got EL84 on the brain there, or sumpin'? ;D

Seriously, your figures were correct for the EL34, and I agree, that extra current draw could have blown the cable connector, but wasn't the amp designed for that kind of draw? I might more suspect the sockets themselves, and/or the grid current limiting resistor (470 ohms, 1 watt), sometimes heat can blow that thing up.

PH, hope you can get back to "normal" living soon! ;D


sumgai

[pollyshero]

EL34, EL84, E-I-E-IO! Thanks for the proofread sumgai. And correcting my own post: "St. Louis Sound" should read "St. Louis MUSIC".

As for above - I think both you and unk are giving me solid probable causes. Keep in mind this is an SLM product & they aren't exactly reknown for high quality manufacturing practices.

I appreciate any input - it keeps me thinking & helps solidify the jello in my head!

[UnklMickey]

sumgai said:

...Whatsa matter, unk, you got EL84 on the brain there, or sumpin'? ;D...

and thats a bad thing?


other possible excuse:


i got fitty cent on the brain and added it to EL34 to get EL84?



"that extra current draw could have blown the cable connector, but wasn't the amp designed for that kind of draw?"

Sumgai, things often fail when operating within electrical parameters that they were "designed for". corrosive enviromental influences, partial damage during assembly, excessive temperatures, and mechanical stress can be factors.

i would be looking for 1 thing that is in common with both output tubes particularly in the heater circuit, since he mentioned they weren't "lit", but the preamp tubes were.

i haven't been inside a BV, but given the small size of the board that the output tubes are on, i suspect it to be a daughter board. the header(s) that connect it to the socket(s) on it's mother would be a likely suspect for failure. my guess is, the contact was poor to begin with, the increases current of the EL34s just accelerated the failure.

as i have mentioned in other threads, troubleshooting by remote control is a tricky business. Sumgai, your suspicions may turn out to be true. "all things are possible" and after all he is in Texas, right?

as far as SLM goes, they distibute Ampeg, so no matter what else they do, they can't be all bad!

unk

[sumgai]

unk,

Points all taken, about remote troubleshooting, etc. And even before adding any extra current draw to fry a component, just plain ol' jostling around could have done the trick. Lowerd knows, I've had more than one amp blow up right in front of my nose after doing something simple like extricate the chassis so I could take voltage readings, or something else equally innocuous. Sometimes the Fickle Finger of Fate wags in my direction, sometimes in yours. ;D

And here I thought that PH was gonna bring a new "sound" to the realm, basing it in St. Louie..... ah well, maybe some other time. As far as I'm concerned, St. Louis Music is a solid 2nd tier provider of good value equipment. I've seen more than one VC5212 or VC5310 come through the shop that stopped my heart with that beautiful tone. But tarnation are those things heavy!


sumgai

[pollyshero]

I guess I should qualify my statements about SLM gear...

I have been a Crate lover since the early days and really can't fault them for much. For the price they are great sounding amps & if not for them a whole lot of folks would have had to shell out the same $ for inferior sound.

I have a VC105 (cranked & mic'd through a PA, it really puts out!), GT50 Stealth (bell tones & crystal clear on the clean channel + squishy saturated 80's metal on the high gain) & the BV6212 (bluesy clean & chunky crunchy distortion).

Problem is, they're built as cheaply as possible which leads to problems that keep them a 2nd tier provider instead of a forerunner.

I have finally decided to quit thinking about learning about tube amps and actually do it. These three promise to provide me many hours of learning experience. But I wouldn't trade them off, and I'd replace them with duplicates if they were lost or stolen.

As for SLM distributing Ampeg - I also have a BA115 (solid state) & haven't had a whit of trouble out of it... Are tubes really that finicky (the Crates), or are Ampegs manufactured somewhere else?

Go figure

[sumgai]

PH,

I guess I should qualify my statements about SLM gear...

I have been a Crate lover since the early days and really can't fault them for much. For the price they are great sounding amps & if not for them a whole lot of folks would have had to shell out the same $ for inferior sound.

I have a VC105 (cranked & mic'd through a PA, it really puts out!), GT50 Stealth (bell tones & crystal clear on the clean channel + squishy saturated 80's metal on the high gain) & the BV6212 (bluesy clean & chunky crunchy distortion).

Problem is, they're built as cheaply as possible which leads to problems that keep them a 2nd tier provider instead of a forerunner.

I have finally decided to quit thinking about learning about tube amps and actually do it. These three promise to provide me many hours of learning experience. But I wouldn't trade them off, and I'd replace them with duplicates if they were lost or stolen.

As for SLM distributing Ampeg - I also have a BA115 (solid state) & haven't had a whit of trouble out of it... Are tubes really that finicky (the Crates), or are Ampegs manufactured somewhere else?

Go figure

SLM farms out the manufacturing of Crate amps to various overseas concerns. Ampeg is still being made on-shore, AFAIK. (But I could be wrong 'bout that.)

And yes, even in the early years of R'n'R, if you played serious bass, you skipped the Fender and went straight to Ampeg, you didn't pass Go, you didn't collect $200, you just went out and got the best bass sound possible. (The only exceptions were bands that had an "appearance' schtick - all the amps and guitars, as well as all the clothing, had to look exactly alike. Many a Fender Bassman (or even a Showman for the bass) did yeoman duty on this front, before being cast aside like so many used boat anchors. If only we'd known back then what we know now, eh? )

IMHO, tube circuitry is not, and by extension, tubes themselves are not, 'finicky' or more trouble prone than any particular class of SS devices. It's a numbers game, and it depends mostly on what kind of money was spent in the first place. You've said it before, right here on this forum - you get what you pay for, and that includes item reliability. The one thing that's different nowadays compared to yesteryear is the number of qualified tube equipment repairmen. More and more, I see guys with great problem solving skills in the SS department just fall apart when they see a tube amp. Not that they wanted to, but they just didn't get the necessary dope when they were in school - "Oh, tubes? Don't worry, you'll never see them, so just shut up and pay attention here." You get my drift, I'm sure.

So, that means that you've got more work cut out for yourself before you can even get started. My best suggestion is to seek out websites that are run by Amateur Radio Operators. Even the new generation of hams are well versed in tube technology, their licensing requirments are still rooted in the 1940's! Books? Yeah, that's a good thing to have a few of around. Again, try for older books that were written by guys who are, as we say, "silent keys". (They aren't living anymore, so they can't pound out any Morse code - their key is now silent.)

Otherwise, just ask questions here, and I'm pretty sure that someone will answer you before you get antsy and stick both hands inside a hot chassis! ;D

HTH!


sumgai

[Ripper]

I too had the same Crate amp. It was the combo correct?
2/12" speakers.

I fried the circuts the first week I had the amp. Had them replaced under warranty. Then I went through tubes like nobodys business.

I must say the amp sounded great when it ran. But it gave me nothing but problems and I sold it within a year.
It was around that time that I went to the hybrid Marshall....never looked back!

I got sick and tired of buying tubes.

[sumgai]

deep,

Constantly failing tubes is indicative of wildly incorrect bias. Your amp should have been checked more thoroughly by the repair station (during the warranty service) before you got it back.

Don't take my word for it, ask Unk, Chris, Channelman, or some of the other oldfartstimers here.


sumgai

[Ripper]

Sumgai...

To me, the great part about the Blue Voodoo was that it was "Self biasing" No muss, no fuss.
I got very impatient and annoyed at that amp. I guess I should have asked someone for advice.

Water under the bridge now.

btw...Your word is all I need!

Thanks again.

[sumgai]

deep,

So called "self biasing" is not a myth, but it falls way short of doing the job correctly, IMHO. Yes, it's been around for many years, possibly longer than adjustable biasing, but that's not the point...... the point is, what does it take to get the best possible tone out of the amp? And the answer is, invariably, adjustable biasing.

The reason? It can be adjusted for one's needs/likes/desires/wants/what have you. It is not a compromise in what the designer thinks is best, which is the case with self-biasing. By doing so, you may alter the overall characteristics in favor of one thing (perhaps tone?), and at the expense of another (possibly tube life), but that's the perogative of you, the owner, not the designer. Who, BTW, will never be in the same room with you so that he can get instant feedback as to what he did wrong. (Like, as in, you choking the s__t out him for such stupidity.)

In my experience, most amps with EL34's are self-biased, and most amps with 6L6's are adjustable. Your amp may have had one, the other, or both, as normally applicable. Hard to tell without a full schematic. (And Unk's original posting actually pointed to a 60watt version, not yours.)

In the end, you're correct, it's gone now, but I do like to keep things clear. The next time you find a "screaming deal" on a similar beast, don't back away because of your previous bad experience. But I'm sure you already knew that. ;D

HTH


sumgai

[pollyshero]

The Blue Voodoo (some say "doodoo") BV 60 and BV6212 are identical amplifiers - the only difference is the cab & extra speaker on the 6212 (which is what I have). My schematic, obtained directly from SLM is for the BV60 - check out the notation! Gotta give 'em props for keeping the printing costs down...



I'm beginning to doubt the wisdom of purchasing an amp from a company that employs people who can't spell "also"

Baahh - SLM and Crate fill a niche and do it well enough - Even knowing what I know now, I'd probably have bought the thing anyway: "Blue-Voodoo" - how cool is that?

Anyway - as I said, I liked it well enough when it was working, and it's providing me an education (well... SUMGAI is providing the education) in tube technology, and the price was right at the time. Headaches, sleepless nights, and mumbling, but no regrets.

Yet.

PH



(EDIT: converted URL link to show the actual image - sumgai.)

[sumgai]

Polly,

(Did you get any of the credit for the new movie that just came out? ;D)

You showed us a partial schematic, and Unk linked to a full schematic. Sadly, as I write this, I see that schematicheaven is down, at least temporarily. So I can't re-verify my memory of this, but it seems to me that Unk's linked image had a Title Block that identified the drawing as a BV-60, but since you're dealing with a BV-6212, I made a rash assumption.......... But more to the point, I am morally certain that the transfromer shown in his linked image had the secondary windings going downwards from the primary, whereas in yours, the the schematic shows them going upwards. At least, I think that's how I remember it.

(Beg your pardon, it's now a few hours later...... The Blue Angels are flying new patterns this year, and they are low, baby, I mean _low!)

I'll cast around and see if I can locate another image like the one missing from schematicheaven. I'm curious to find out if my short-term memory is getting that bad already. I was so banking on at least a few more years.


sumgai

[ampedup]

Hey PollysHero, ya get that BV-60 back in action yet? I've got one on the bench now, and I sure could use a copy of that schematic!! Check my profile for my email address. Here's a tip for ya. The 6A filament fuse F4 is underrated. It should be a slow blow too. With the stock tubes (6L6) I am measuring 1/2 an ohm with the tubes cold. 6.3/0.5=12.6 surge current. The amp in question would sometimes light the fillments and sometimes not. I shook the filament wires and it "fixed" it. Wrong. Seems the heat stress on the fuse worked it loose and it was making intermittent contact. I'm hoping a 5 amp slow blow will work for both 6L6 and EL34 (calculating 4.5A total with the EL34). Got a 5 amp fast in it now and you can really see it sag when the juice hits it... So guys if ya got a Blue Vodoo with the lights on but nobody home, look at F4.

[pollyshero]

~sigh~ Life intrudes... Still just a mess on the bench I haven't cleaned up yet. I let myself get distracted by an evil mistress in the guise of an '86 Toyota MR2. I know I should let her go, but she's so sweet...

I'll give F4 a look - thanks for the tip.

PH

[pollyshero]

Well...

I've been taking my time & only working when I felt like it. I completed tracing every circuit this weekend, and couldn't find any loose/broken connections. All resistors checked out OK in that they were within ten percent of their rated marking. I did replace a few here and there because they weren't the value specified in the schematic. All the electrolytics charged and discharged, but I can't tell if they're operating within parameters. I just kind of went with the assumption that as long as they "worked", it ws good enough for my current purpose: just getting the thing to light up.

Anyway - Put it all back together & fired it up. Same old story - none of the tubes would light. I checked all the heater voltages at the tube pins & they were all very low - like .3V (should I have seen 6.3V or something closer?). I checked for 6.3V at the board terminals where the wires from the PT connect and got slightly higher readings, but still no soap.

Within seconds of checking for voltage at the terminals, the thing lit up! Very scratchy & crappy sounding, but the genie in the bottle was dancing. I checked V at the tube pins again and was seeing 2.5 to 3.2VAC.

The power tubes and all four 12AX7s were lit nice and bright, but the single 12AU7 (reverb driver?) was a bit dim. Also had a microphonic effect - it was either the 12AU7 or the first 12AX in the preamp: hard to tell from tapping. I checked the voltages at the test points indicated on the schematic and was coming up just short of specification, with the voltage dropping the closer I came to the 12AU7.

I left things burning for about 30 minutes & then shut her down for a few hours. When I came back & switched on, I was back to square one - none of the tubes lit.

Remembering that the 12AU7 was the only one that wasnt lit fully, I replaced it with a new one and...

As of 30 minutes ago my neigbors weren't too happy. It currently performs as it did before I swapped in the EL34's and the problem cropped up. If the deity of my choice is kind enough, perhaps it will continue to work.

But I'm all empty inside... I easter-egged all the tubes (including the 12AU7) previously with no result. This thing has been on the bench for damn-near 6 months. I've learned some very valuable things. But for what? It didn't work before. It does now. But WHY???!!! HOW???!!! Was it a loose connection at the board terminal coupled with a failed tube? or what? AAUUGGHH! again

Oh well. I'll look the gift-horse in the mouth while my ears bleed!

Thanks ever so much for putting up with this mostly ho-hum post. Sum, Unk (if you're out there, please let us know - we miss you), Amped: Thanks for your input.

Cheers

PH