Blue Voodoo 120 Noise Problem UPDATE: GOOD NEWS TO SHARE!

[plexi50]

Hey all! I have this blue voodoo 120 that i have had for a while now. The noise (hum / hissing) this amp has is a real irritating thing

I have gone completely through the amp and have made some preamp plate resistor changes in the dirty channel

I was just looking at the schematic and i see that the filter cap that supplies V1A is 10uf / 400VDC

Should not that 10uf 400VDC Cap be in the 30+ uf range? I am also thinking the FX loop and L pad section might be to blame

I have the amp sounding great but this hiss is too much to bare

[HotBluePlates]

Not necessarily.

It seems to me like most Crate stuff has way too much gain. Are you sure the noise isn't due to too much gain along with maybe poor pc board layout? Does the amp really hum/hiss on the clean channel?

[plexi50]

HBP it does hum on the clean channel as well. But no where as bad as the dirty channel. Funny thing is when i plug a patch cord into the FX loop return the amp is dead quiet and if you touch the tip you have a very clean signal

If you look at the FX Loop/ pad and OP amps, im thinking this could be where all the hum and hiss is coming from.  If i disable the FX or rewire it minus the L pad straight from the master and through the send and return jacks back to the PI that would either rule out or condem the FX OP amps i suppose

But yeah i see what your talking about with the preamp. Maybe i could run a cord from the send to another power amp and see if the preamp is noisy and the problem. Im just throwing things around in my head right now but it's a start

It would be nice to finally solve this particular known problem with these amps. All the preamp cathode values are 1.5K / 2.7K and such



 

[HotBluePlates]

Well, it sounds like you have a clue with the effects loop.

[plexi50]

Man i dred pulling this board out again. It's not that bad but it's a fragile board.

[plexi50]

FX Loop is fine. Reverb is fine. Removed 2 power tubes and hum gone. One of them is picking up transformer or PS frequencies. Touched one of the 6L6GC tubes and it squealed so i decided to remove the two outer tubes to see what would happen. Actually sounds better too. Will stick in 2 more power tubes when i get the energy and see how they sound

[plexi50]

Ok* I found what i think is the real hum issue problem in the Crate BV120 amplifier

I dont fully understand how this part is making hum BUT: Cut out that big black part SIDAC 120V #TR1 wired to the heater circuit

Hum completley gone from amp. This is a new amp now. Before the amp would hum with out any guitar plugged in

Guitar plugged in and still dead quiet except for the usual slight hiss you may get at high volume levels but it's very negligable

A small amount of negligable hiss is better than the amount of pure annoying hum this thing was putting out

The amp is usable now as any quiet amp should be. Can anyone explain what TR1 was doing in the heater circuit? I am amazed!

It has been bugging me for years why such a good sounding amp after EQ & Plate changes would have all that hum in it

HPB asked earlier if this was maybe just a bad layout and being such a high gain amp that maybe it just was what it was

I cant believe i found this little irritating problem that still dont make sense. The part itself does not even need to be in the circuit as far as i understand heater filiment circuits

Before snipping the SIDAC off the board i got no AC voltages on pins 7 of the power tubes to ground

Across pins 2&7 i got 6.00VAC

Now i am getting 3.29 on pins 7 of the power tubes to ground and 6.25 across pins 2&7

I have been reading for years about how after these amps warm up the hum would increase and get louder

I found this online. Why did Crate use this part?

The SIDAC is a silicon bilateral voltage triggered switch with greater power handling capabilities than standard DIACs. Upon application of a voltage exceeding the SIDAC breakover voltage point, the SIDAC switches on through a negative resistance region to a low on-state voltage. Conduction will continue until the current is interrupted or drops below the minimum holding current of the device.

[Tiny_Daddy]

That part must have shorted. Thanks for sharing!

[plexi50]

That part must have shorted. Thanks for sharing!

Yes on the being shorted. Why have it in the heater circuit? Is this part unstable which causes variable heater voltages?

[PRR]

> Why have it in the heater circuit?

Darn good question.

All I can think: check-box design with idiot criteria. Since the heater system is not "hard" grounded, someone thought it could float to arbitrary voltage (despite the 470 and 330 resistors). The 120V SIDAC would "trip" at 120V and pull one side of heater to 1.5V.

And 120V across the 470 330 network is 1.24A, not-much over the 0.9A rating of the SIDAC.

If it did see steady 1.24A, it WOULD melt, probably permanent-short. And now the "balanced" heater feeds are strongly UN-balanced and not even sine-like. BUZZZ!

But I just can't see how that SIDAC could EVER see 120V before big sparks happened elsewhere.

As you are saying: NObody else does it this way. Snip it and call it done.

[Tiny_Daddy]

I agree, probably drawn up by someone not used to designing with tubes. Anyway it shouldn't have shorted. Don't know how that could happen.

[plexi50]

Well at least i have a happy amp again. Not that i use it that much either. It's more of a wall fixture. A big night light

I kept looking at the schematic and thought this part wont stop the amp from working

So i decided to see what would happen if i cut one leg and presto the hum was gone

The 120V rating looked odd. Anyway 

[HotBluePlates]

I kept looking at the schematic and thought this part wont stop the amp from working

So i decided to see what would happen if i cut one leg and presto the hum was gone

Where's Muntz when you need him?

[plexi50]

I kept looking at the schematic and thought this part wont stop the amp from working

So i decided to see what would happen if i cut one leg and presto the hum was gone

Where's Muntz when you need him?

There ya go!

[ctravis595]

Hey so I removed the 120v sidac at the tr1 position and thought the amp sounded a little less noisy but after three light practices, my amp doesn't make noise. Took it apart to find out a resistor on the power tube circuit board blew( burn marks, resistor literally broke into pieces)

Does anybody have any insight as to how removing the 120v sidac caused this to happen?

[PRR]

> a resistor on the power tube circuit board blew

Which one?

[plexi50]

Does anybody have any insight as to how removing the 120v sidac caused this to happen?

What makes you think that removing the 120v sidac caused a resistor on or near the power tubes to burn open?
Just asking. The power tubes screen and grid resistors have nothing to do with the AC filament winding or DC filament string

Bad power tubes can  blow,crack,burn a screen resistor. Do you know what numbered resistor it is on the schematic?

[ctravis595]

oh wow didnt see you guys replied so quickly

i talked to an amp tech and he thought the same thing, a power tube can cause what i'm talking about although -

my tubes are fairly new (one month old, maybe 24 hours on them altogether) and they were matched before shipping

since i messed up my blue voodoo i picked up a mesa nomad 100 head(can switch between 6l6's and el34's), so i threw the new 6l6's in there and they all light up and sound great, so i don't think it's the tubes themselves

i only think removing the 120 sidac caused my issues because it happened very shortly after removing the 120 sidac

here's some pictures to help clear up any discrepancies. one of the sidac removed and another of the 3 resistors that went bad on the power tube board





since then i've picked up a soldering gun, some solder and the smaller resistors i found at radioshack. i ordered the 470 Ohm cement block resistor also. i'm having trouble finding the 120v sidac online though. i'm gonna try to replace everything how it was and put the amp back together to see what happens

[ctravis595]

ultimately, now i think it would be cool to run a splitter from my guitar into both the mesa and the blue voodoo head and have them simultaneously run into my v30 stereo cab, maybe i could get an awesome blended tone between the two, i always remember the low end being really muddy on the blue voodoo, while this mesa sings low notes with ease no matter what volume

[plexi50]

The burnt grid resistors R201 & R202 are a mystery. Did a power tube with broke off guide pins ever find it's way into your amp? Charred bias grid resistors i believe would be a tube or contact with a high voltage source. Did your power tubes ever red plate? If the coupling caps were bad and the bias was allowed to run away for an extended long period i think you may had smelled something getting real hot.
I dont know how bias grid resistors could flame up like that except by a tube put in the wrong way.
Is there a missing ceramic screen resistor there just above R201 & R202?

[ctravis595]

I don't think they were burned out before removing the 120 sidac, the thing that puzzles me is why the amp worked fine for a few practices and I even noticed reduced noise, but then after third time using it, it dries? If I remember correctly I think I rushed the warming up/ cool down period before and after use of tube amp

The 6l6's I have are in good condition

Altogether there are three burned out resistors, a big rectangular cement one, and two of the smaller color codes ones

[plexi50]

a big rectangular cement one

That is a screen resistor. And IMO it went open from either bad luck but more realistic from a power tube  that went south on you. Thats why the screen resistor is burnt open with no reading on your DVM, meter. The grids as well got zapped buy the tube when it went south as well. I have seen charred grid resistors before only once. I believe your power tube or tubes went North,South,East and West when it shorted out taking out the grids as well

Just because a tube may work in another amp or even read good on a good tester does not mean that the tube structure internally is good. It can be loose and just barely functioning. A test i do is when i have a power tube that is suspect, i flick it with my finger when in the short testing mode on my tester. This sometimes will shock the tube enough to create an intermitant short and only then will it show itself when the short light or meter starts to float around on the scale. If you see any white,silver flakes floating around inside a power tube you can bet that it has seen a good amount of use. This alone does not mean the tube is bad but a good indication of bad things to come at some point in time.

Question? Do all of your tubes filaments in that amp light up?

[ctravis595]

yeah so one bad screen resistor and two of the smaller color coded ones

soldered both back on and reassembled the amp. ordered the sidac but i've yet to install it. amp cranks without the sidac so it seems the removing the sidac was not the source of the problem

here's a clip of me playing the same rythmn riff over my blue voodoo (plus vintage mxr 6 band eq and decimator noise pedal in effects loop) with 6l6's and then me putting those same 6l6's in my mesa nomad 100 head (no pedals but 5 band graphic EQ)

tell me if you can spot the crate vs the mesa, which one is which?

https://soundcloud.com/cody-dwayne-travis/bluedoodoovsnomad

[plexi50]

You DO NOT need the Sidac. Removing it had nothing to do with your burnt grid and screen resistors. You need to confirm your work and reason why those resistors burned up. A bad power tube i believe was your problem. You need to find that tube,test it and then throw it out before it finds it's way back into another amp

[ctravis595]

same thing happened again. no sound and two of the lights behind the tubes are out

gonna take it apart tonight and see what's up. if the same thing happened again i'm just gonna throw the sidac back in there

[plexi50]

Re-read this thread. The Sidac has nothing to do with your problem. Why do you think the Sidac is the problem? That part of the transformer,filament winding and artificial heater CT resistors have nothing to do with your screen,bias grid or high plate voltage board. These amp boards are very flimbsy. Has it been worked on before? Tube tester? OT bad? Bad arched power tube socket? You need to answer these questions before blindly assuming what may be bad. It's a process of elimination from your secondary B+ throughout the power supply resistor nodes and PS capacitors. Supply some more pics of the entire power tube board. I suspect it has been worked on in the past and solder is connected to one of the power tube board pins that connects the tube board to the two connectors after you push the board in place

[ctravis595]

i've read through this thread probably 10 times now, 8 before i did the mod and twice afterwards just to make sure i did everything correctly

i'm no electrician, my "handiness" is all self taught and i mostly work on vehicles rather than electronics. it just doesn't make sense the amp worked for years without any kind of issue, then i remove the sidac and i'm now i just happen to be consistently blowing resistors?

when you make a modification on a car and then the car doesn't start, it's only natural to think whatever you modified is causing the no start condition right? i'm applying this same logic with my amp problems but it is possible the problem lies elsewhere

the amp doesn't look like it's been worked on at all actually. you can tell it's been opened up before but i think that's merely just to adjust the bias. nothing looks modified on the circuit boards or "resoldered" or anything like that (besides the new resistors i threw in)

i made sure to line up the pins correctly also

i'll try to get some more detailed pictures

i have no tools to check the tubes, i ordered a matched set so i could try to avoid having the thing biased. perhaps an incorrect bias setting could cause these resistors to blow on my power tube board?

OT bad? i'm not entirely sure what OT stands for

i saw no evidence of arching on anything on the power tube board (just the black burn marks from the resistors frying)

[plexi50]

Were the power tube guide pins ever broke off and re-glued to the bottoms of the power tubes or tube? Look close at the base of the guide pin. The guide pin knotch should be located just between pin 8 and pin 1 of a octal 8 pin power tube. Some tubes dont have the numbers on the bottom so you will have to locate them. Sidac again has nothing to do with your current problem. Murphy's Law

[ctravis595]

ok fell off for a bit, to be frank i got kinda frustrated that all the new resistors kept burning out so i just ran the amp on two power tubes instead of four and it works. still need more headroom to be used live

plexi50, sorry if i came off as not very attentative, or thick headed. i just looked over the entire power tube board multiple times, no stray solder, no bad solder joints...i can't find anything. i'll post some more pictures though if needed

all of the guide pins on my tubes look good, not to be rude but i feel i would've definitely noticed a bad guide pin or a lack there of. i'm very gentle putting in and pulling out my tubes as i know these boards can be fragile

i agree the sidac is not the issue, i was more saying that the issue only happened after the sidac mod.

my next plan of action is to start testing caps correct?

[ctravis595]

i also tested the amp with 4 mesa 6l6's and had the same results. i was actually able to watch the tube, and its flashing blue for a second when i have all 4 power tubes plugged in. almost like the tube is getting way too much voltage. explaining the screen resistor getting too much voltage, explaining its failure

so somewhere between the power supply and the power tube board, is a bad resistor or capacitor im guessing. sounds like a guessing game with the voltmeter is in session

[HotBluePlates]

... all the new resistors kept burning out so i just ran the amp on two power tubes instead of four and it works. ....

my next plan of action is to start testing caps correct?

i was actually able to watch the tube, and its flashing blue for a second when i have all 4 power tubes plugged in. almost like the tube is getting way too much voltage. explaining the screen resistor getting too much voltage, explaining its failure

so somewhere between the power supply and the power tube board, is a bad resistor or capacitor im guessing. sounds like a guessing game with the voltmeter is in session

No, don't waste time testing caps. Don't waste time guessing. Understand how the circuit works and what the resistor destruction tells you.

Current burns resistors, when there is much more than designed. Another poster said the resistors burned were 2 control grid resistors and a screen resistor. Unfortunately, the Crate schematic shows everything except the output tube sockets and the resistors attached to them, so I can't verify the above.

So the screen resistor for that (pair of?) tube(s) passed excessive current and burned. That could happen through normal use at full power output (during the instant when the plate current for the tube is at its peak) but is very unlikely because the designer would have taken care of that in the design, as it's "normal use". If the control grid was driven very, very positive then the resulting high peak currents could include a high enough screen current to burn a resistor. However, this too is very unlikely, as the circuit isn't capable of driving the control grid positive-enough in normal use to cause damage this way.

The 2 burned control grid resistors are a clue. The control grid passes essentially zero current at all times under normal operation; there is some current in maybe the micro-ampere ange and would have to be a thousand times bigger to even register on your meter's most sensitive setting. So a current big enough to burn resistors is nearly impossible...

Unless... the screen voltage on pin 4 of the output tubes (about 450v) is able to come in contact with the control grid at pin 5 (and its bias of about -50v). If these two points came in direct contact, then the high current would flow through the screen and control grid resistors and probably burn them open before any serious damage occurred to the tubes. The resistors would have about 500v across the pair of them (450v + 50v) which could flow enough current to burn them open.

The output tube socket sits nice & high off the board. There's plenty of room for a bit of metal, loose solder blob or wire/component lead fragment to find its way over to the socket and touch pin 4 & pin 5. But that does seem like a one-time failure, given you don't see a bit of metal bridging those two pins in your picture, and the fault happened multiple times.

Turn the amp off, unplug it and measure the power supply voltage to be sure it has dropped to 0v across the board. Switch your meter to resistance mode (or continuity) and measure directly from the "bad tube socket" pin 5 to pin 4. Even if you get no continuity, re-check on resistance mode, as anything substantially below infinity Ω probably indicates a fault.

I suspect that the first occurrence happened when a bit of metal that you snipped (or was otherwise loose in the chassis) just happened to bridge those pins on the tube socket. The excessive current may have damaged the board itself or burned a carbon track enable a recurring short-circuit, which could account for the follow-on burned resistors. Or maybe something else happened...

Either way, start your tests directly at the fault, looking for the most logical way for all clues to happen together.

[ctravis595]

putting the negative probe in the pin 5 and the positive in pin 4

no readings on AC current

on resistance however the two tube sockets closest to the speaker outputs both read roughly .30 while the other two furthest away register off the chart (infinity i guess)

sorry if my readings are inadequate im new to using the voltmeter on amps

edit ( the fact that two power tube sockets give bad readings and the other two don't lead me to believe the fault is around that area)

is there anywhere i could just order a new power tube board from?!

[ctravis595]

i also inspected for loose metal and found none

but elaborating on that theory, perhaps some metal is bridging something underneath the main PCB (Rather than bridging the power tube PCB board)

i've never taken out the main PCB...

[HotBluePlates]

putting the negative probe in the pin 5 and the positive in pin 4

no readings on AC current

Ugghhh! A meter's current setting creates a short circuit from the red lead to the black lead, so current will divert through the meter for measurement. So don't ever do that for 2 points you know to be at different d.c. voltages.

putting the negative probe in the pin 5 and the positive in pin 4

... on resistance however the two tube sockets closest to the speaker outputs both read roughly .30 while the other two furthest away register off the chart (infinity i guess)

The good tube sockets measure properly, the bad tube sockets measure as a short-circuit. So there is a short-circuit from pin 4 to pin 5.

Now your problem is to figure out where that short circuit is.

• Could be a bit of metal touching the socket pins (but you didn't see any).
• Could be a short circuit on the underside of the board between those two solder pads.
• Hopefully you pulled the tubes out of those 2 sockets, or it could be a short internal to the tubes (very unlikely to have 2 tubes with the exact same internal short at the same time).
• Could be a short circuit at some other point along the traces that run to those 2 tubes' pins 4/5.

You'll probably have to pull the board and do a LOT of careful inspection and resistance checks to figure out where the short is occurring.

[ctravis595]

err sorry for my ignorance, glad to know i am actually indeed working with DC and not AC. i just assumed amps worked on AC since they can utilize power conditioners and work from wall outlets

but the power transformers in amps explains the ac/dc thing (no pun intended)

thanks for the guidance thus far, i feel like i am definitely getting closer to sorting this out

a weird occurence i think you'd find interesting -

i read for 5150's if you read resistance between pin 4 of each tube socket it will tell you whether the screen resistor is working properly

(no particular order) but i get similar readings between socket 1 and 2, socket 2 and 3, but NOT socket 3 and 4

seems theres a faulty screen resistor on the power tube board that i was previously overlooking?

it just makes a lot of sense to me

edit :sorry if this is confusing, what i mean is the physically burned resistors i was replacing were in the very middle of the 4 power tube sockets, where as my latest test is pointing to issues inbetween power tube 3 and 4 sockets if this makes sense. although ive inspected i have not run tests on these so maybe thats where the fault is

ive also since picked up some mesa 6l6's to test with the blue dooodoo with the same results so i know its not tubes and just the board at this point

[ctravis595]

testing between pin 4 of the power tube sockets is giving me a 950 reading on resistance

testing each resistor by itself - two of them are giving me 470 while two are giving me no resistance readings at all


a quick google search shows that something is indeed shorting out these resistors (giving me no reading) but they physically look fine


i also dont see where on this power tube board anything could short circuit (no solder connecting two pieces of metal, no overwhelming corrosion) but at this point i guess it could just be the harsh soldering work on this fragile board

tell me if you see anything that would cause short circuiting, i know it looks super shitty but it still works soldered up like this with the two power tubes (rather than the 4)

[sluckey]

two are giving me no resistance readings at all

There is a big difference between "no resistance" and "zero ohms" resistance. No resistance is infinity ohms, an open circuit. Your meter shows "no resistance" when the probes are just hanging in the air, not touching anything. A short circuit is zero ohms. Your meter would show zero ohms (or very close) when the two probes are touching each other.

So, with that info, tell us, what is your meter telling you, no resistance, or zero ohms?

I suspect the resistors are open, but only you can confirm that.

[ctravis595]

no resistance. there is no change from the reading when the probes are dangling in the air and from when they are probing the tube socket

[HotBluePlates]

I've probably reached the limit of what I can troubleshoot on this amp without having it in-hand; but I'll tell you what I think I see.

For now, the outside stuff about the screen resistors is probably not helpful for you. From the evidence you found earlier and posted here, there is a short-circuit from pin 4 to pin 5 on the two bad sockets. What does that tell you?

The average repairman would know pin 4 is the tube screen and pin 5 is the control grid. They'd also know that screen voltage is usually several-hundred volts and close to plate voltage in most amps (in the 450v range in your amp) and that the control grid is negative and around -30v to -60v in many amps (assuming they use fixed bias). They would additionally know that there is no part in the amp that forms a direct connection from the positive screen voltage supply to the negative bias supply, so the search for a single failed part will almost certainly bear no fruit.

What does that leave you? You should be looking for some kind of physical connection from pin 4 to pin 5 (or the traces which run to them). Notice how the board has cuts between some of the tube pins? Crate already recognized the possibility of solder blobs on one pin bridging to the next pin (or leakage due to solder flux all over the board) and cut those slots to minimize the risk.

In your pictures, I see one point where a solder pad which ultimately connects to one of the shorted pins sits VERY CLOSE to the trace running to the other shorted pin. I also see a nice big solder blob, which ordinarily wouldn't matter because of the green solder mask covering the trace. But nearby your amp appears to have solder mask burned away from traces or scraped away from traces. See the pic below for one of these areas circled.

So that point appears to present a risk for a physical short-circuit that normally couldn't happen, but can now because of a combination of the unique layout of that amp's board, damage to the solder mask, and the degree of excellence of the soldering. I'd suggest removing the resistors, using a solder sucker or solder wick to remove all the solder from that spot, use some kind of flux remover to clean up the board. Then re-measure resistance from pin 4 to pin 5 of the bad sockets to see if you can eliminate the short circuit. If you work one solder point or one component at a time (yes, it takes longer this way) then you will know exactly where the short circuit occurred.

[ctravis595]

you are extremely helpful thank you

[ctravis595]

so i was able to figure out the problem and why it wouldn't go away

the issue wasn't the bad soldering on the power tube board (to my surprise) and there was some burned trace on the main PCB board for the amp. i never took it out before now so i didn't know. i cleaned the burns and powered up the amp, the tubes light up! guitar plugged in and its sounding sweet (even with these terrible mesa tubes)

now here's my new dilemna - (of course its not over yet)

whenever i play with all 4 6l6 power tubes in, resistor r92 starts to smoke and smells like its burning. when i take out the middle two power tubes it no longer does this and seems like it can be played for a while

ultimately i would like to get this amp back to 100 watts reliably. does anyone know why r92 is being burned with all the tubes plugged in? gonna reference some schematics and see what i can figure out but i have looked over these boards top to bottom for bad solder joints, burned trace and burned resistors to no avail at this point

edit - i have not biased the tubes yet, maybe this is cooking them and the r92 resistor. one of the tubes glows a little blue

there's also a somewhat faint popping noise when the amp is one but there is no guitar playing, with playing it isn't heard

excuse my terminology but after referencing the schematic it seems r92 is by itself in line with the entire power switch circuit

https://dl.dropboxusercontent.com/u/77904849/105XXH1.pdf

-schematic, r92 is in the very top of first page

-short version - got the amp to work again but only with two power tubes instead of 4, 4 power tubes make resistor r92 start to burn

[John]

Measure the voltage drop across R92. The schem says it's only 2 volts (460-458). If it's burning, it's dissipating more wattage than it's rated for, and you need to figure out why. The popping sound you hear is probably a clue, but I don't know enough to tell you what it is.     But simply putting in a higher wattage resistor won't fix the reason that there's so much current being drawn.


It seems like if your tubes were biased *that* hot, (sucking lots of current) they'd be red plating long before that resistor started smoking. So, check for shorts right after that R92. Maybe filter caps are leaking .... although pulling 2 tubes shouldn't make a difference then....


Oh, if you don't have a light bulb limiter, build one (it's quick and easy) and that'll let you know if you've got a short somewhere for sure.

[Willabe]

Oh, if you don't have a light bulb limiter, build one (it's quick and easy)

Here's a link to Sluckey's web page of how to build and use a light bulb limiter and he has lots of other great stuff in there too!

http://home.comcast.net/~seluckey/amps/misc/Amp_Scrapbook.pdf


               Brad     

[PRR]

A powers the Plates, then R92, then B powers Screens and everything else.

It takes 182 mA to over-heat a 150 Ohm 5 Watt resistor, simple math.

6L6GC at high output, the screens can draw 22mA per pair at max signal. 44mA-60mA would seem to be an upper guess for a quad working very hard.

"Everything else" can't suck big current because there's other resistors in series. Notably R94, 8.5K 5W, which would be cooking at 24mA.

The MOST likely problem is a bad 6L6 with a screen grid short. Replace it.

[ctravis595]

the tubes are fine

so i should be looking for a resistor not doing it's job correctly? presumably a resistor on the power tube board?


major thanks to everyone in this thread, i have learned a lot

[plexi50]

Please tell us if you are using new tubes or the ones that came in this amp/

[mrr3000gt]

Bringing back the dead (thread) on this one: in case someone finds it looking for similar issues.

Great Blue Voodoo info here. I actually have one and wondered who on earth would use a SIDAC for what it is doing in this circuit when I was looking how hum balance was implemented in my amp. Fortunately the SIDAC was not in the revision of the BV60 combo I have but was in the BV60H (head version) of the schematic.


My version of the BV60 appears to use a hum balance pot in replacement with the role R118/R119 & R120/R121 plays in the newest revisions of the BV60 circuit.