Voltages Low On V1 - TMB Side A Bit Weird

[KingCrimson]

My TMB side is STILL acting a little strange after my rewire. I'm hearing a bit of distant sounding rumbling and mixed with hiss. The normal side seems fine. I did a voltage reading and I believe the issue is V1. Notice how low the readings are on my V1 as compared to when I first built my TMB. I've noticed that the V1 tube is still microphonic at higher volumes, especially on the TMB side. This is the case even after switching tubes around. I suspect the problem must be something directly connected to the V1 pins on the board. The only big difference on the board is the 220k I have connected to the 6 pin on V1. I doubt this would drop it down to 84.8 as opposed to the original 134 reading though. By the way, I DO already have the resistor on V3 tied directly to the pin via shielded wire.

Any clues much appreciated. But the other tubes' readings seem a tad low, but mostly normal. See chart below.....especially the After Rewire V1 readings.

ORIGINAL READINGS……………….READINGS AFTER REWIRE

V1 …………………………………………………....V1
1=179.7 ……………………………………………1=130
3=1.8 ……………………………………………….3=0.86
6=134.6 ……………………………………………6=84.8
8=1.0 ………………………………………………..8=0.60

V2 ..................................................V2
1=193.5...........................................1=186.5
2=38.7 ............................................2=34.6
3=79.2 ............................................3=72.0
6= 193 .............................................6=187.5
7=37.4 .............................................7=34.4
8=79.2 .............................................8=71.6

V3 ....................................................V3
1=127.5 ............................................1=129.6
3=0.9 ................................................3=0.86
6=262 ................................................6=251
8=132.3 .............................................8=135.5

V4 ......................................................V4
3=12 ...................................................3=11.73
7=341 ..................................................7=331
9=328....................................................9=318

V5 .........................................................V5
3=12 ......................................................3=11.82
7=342 .....................................................7=333
9=329 ......................................................9=320

RECTIFIER............................................RECTIFIER
1=294 (AC) ..........................................1=286
3=351 (DC) ..........................................3=343
7=292 (AC)............................................7=286

[KingCrimson]

For now I've come to my own conclusion that the voltages are weird because of the different resistor values I put in those areas that are normally there.

For instance, V1 (pin 1) has a 110k, and V1 (pin6) has a 220k, the latter being suggested by Jersey Aaron.

I'm going to redo my input wires into V1. I don't trust all of that shielded wire and grounding the wires and this and that all at V1. But I'm only going to do the TMB one because that's the issue.

I'm gonna beat this thing, you guys watch.

[markd]

KC,
Looking at your voltages on V6, the B+ voltage has dropped 8v after the rewire. Changing a few resistors isn't going to account for that. That can only be caused by an additional current draw (or a different rectifier tube). Increasing the value of the plate resistors on V1 would tend to decrease the current draw.
You are on the right track to check all the V1 connections particularly around the TMB section. When you pull the tube in V1 do the B+ voltages go up? The change in plate voltage and cathode voltage on the TMB section of V1 can't be accounted for by changing the plate resistor from 100k to 110k.
Also, on the Normal channel section of V1, I would change the cathode resistor to 1·5k from 820. That cathode voltage is too low.
markd

[KingCrimson]

Could it be these resistors I didn't replace that are still CC? I fear that from all of the soldering, desoldering and resoldering these guys have endured that they may have heat damage of some sort.

[KingCrimson]

KC,
When you pull the tube in V1 do the B+ voltages go up?

I'll check this a bit later. Where is the best place to check for the B+? Would it be at the cap can?

Also, on the Normal channel section of V1, I would change the cathode resistor to 1·5k from 820. That cathode voltage is too low.
markd

I will change this, but my normal channel sounds fine. But things can always be better. Otherwise I wouldn't be trying to perfect all of this. Uggh, the Kiwames are so hard to order and wait for. I'll just get some metal film at radio shack for that 1.5k.

By the way, I haven't switched the rectifier or rewired anything on it.

Another thing I did do is yank out the output jack you see on the right side that I don't forsee using anytime soon. I didn't want the chance of any extra noise it could have been generating from interfering with other wires and such. If any of you out there are weeping now because I no longer have an 8ohm output jack, that's just TOO bad. You'll have to pick up the pieces in your life and move on.

Thanks for your help on this Mark.

[KingCrimson]

Weird. For some reason all my voltages are back to normal, even on the rectifier, but they are still low on V1.

Now V1 is SLIGHTLY higher at

1) 132.8
2) 0.91
6) 89.2
8] 0.62

I have no idea why my voltages on the rest of the amp would be back up to their previous reading before rewiring.

When I pulled the V1 tube, there was no change at the rectifier voltage. At the cap can, either side only was raised by 2 volts after pulling the V1. (left side, 354 to 356.......right side from 332 to 335).

Where would some of you guys begin ripping out and redoing to normalize the V1 voltages?

Also, the TMB side still has some sort of extra white noise sound or very distant crackling/interference.

How can the rock world survive with this issue persisting?

[KingCrimson]

I don't think my assumption listed above about the old CCs is correct. Those go to V2.

What I AM going to redo tonight is these solder connections leading into V1. I have yellow circles around them.

If someone wants to stop me from doing this, it's too late. Although I have no idea what I'm doing, I have a feeling it's going to fix the problem.

[KingCrimson]

DENIED !!!!!!!!!

Oh well, back to the drawing board.

[KingCrimson]

I tried other things, but no luck. I mean, it's not like I turn my amp on and it squawks like a sick bird or anything, but it just doesn't seem as healthy as it should be.

But anyway, here's a photo showing the before and after voltages going through the resistors on the board. These are the resistors leading to the pins in question on V1 that are too low in voltage.

Surely someone can point out what direction I should go with this. It's actually beginning to make me a bit angry. I may just go get some cheap resistors to replace the several to see what happens. I can't figure out if this is the root of the problem, or if it stems from before this.

Are these voltages of 255 too low before these two resistors?

[2BDH]

Maybe you might want to shorten those antennae , I mean grid stopper 68k resistors on V1 a tad lol.

Brent

[Plexi]

""""but they are still low on V1""""

When useing the 820ohm cathode resisotr,and 220k plate resistor,the voltage you have is probbly correct..it may vary a little with different tubes used. But will stay around the voltage you have there. Also useing these values,the amp may have more hiss.
I hate to suggest resistor value changes,since you have those new resistors. But if you change the 220k to 150k or less,the voltage will come up over 100v..or if you bring the cathode up to 1k or 1.5k it will also bring the voltage up some.
You may also have some oscilations that are causeing the voltage to change some or drop. Keep the volume controls down and measure..then measure with them turned up..see if they change..if they do,then you will have to find where the oscilation is coming from.

Richie

[KingCrimson]

Maybe you might want to shorten those antennae , I mean grid stopper 68k resistors on V1 a tad lol.

Brent

Those are only affecting the normal channel, which isn't a problem. But yes, I thought about those leads when I did them. I was sick of having things so crowded, so I left some room to get in between and around things. But I'll shorten them just for you, Brent.

[KingCrimson]

Also using these values,the amp may have more hiss.

I'm changing them out then.

But if you change the 220k to 150k or less,the voltage will come up over 100v..or if you bring the cathode up to 1k or 1.5k it will also bring the voltage up some.

Is it really a problem that the voltage is that low? Someone above said the resistor values I have now wouldn't affect the voltage that much, but you just said they are....hmmmmm. I'm gonna have to believe the the amp builder for American Minor in this case.

You may also have some oscilations that are causing the voltage to change some or drop. Keep the volume controls down and measure..then measure with them turned up..see if they change..if they do,then you will have to find where the oscilation is coming from.
Richie

I've chopsticked my amp to death looking for where the distant rumbling/white noise sound is coming from on the TMB side. It's not bad at all at reasonable MV or volume levels, but anything past 5 on the MV and 7 or 9 on the volume, it becomes apparent. But I'll switch those values today if Radio Shack has those values, and I'll also check for voltage change with different volume levels.

Thanks guys.


UPDATE: Just checked the voltage at volume all the way up and down on both channels, and there is no change in voltage when this is done. I guess that rules out oscilation problems.

I figured out why sometimes my voltages at the rectifier are sometimes normal and then sometimes low - I believe it's because the wall voltage here is 3 to 5 volts higher during the day. But that's not a major issue here, but it had me wondering why the voltages would vary that much from day to day measurements.

[KingCrimson]

Just switched out the V1 resistors; the cathode to 1.5k and the one that connects to pin 6 to 100k (down from 220k).

Anyway, the voltage at pin 1 is still around 130. However, the voltage on pin 6 shot up from around 85 to 160 !!!. That seems a bit extreme, but I could be wrong.

I'm probably making a big deal out of nothing here. Ritchie Blackmore would probably love the tone of this amp, but I'm just being a nitpicking psycho about things that probably aren't that big of a deal.

I'm gonna leave it alone for awhile and just jam with it more probably tomorrow at full volumes to get a feel of what REALLY matters, instead of little stupid things I'm obsessing over in a quiet room with no drums or general mayhem happening.

[Plexi]

Since you only changed values on the one side of the tube,or channel, those voltages are what changed..the other side may change slightly,since the other side voltages have changed. Anytime you change a voltage somewhere in the amp,the other voltages will also change a little. 130v is fine. 160v is also very good here. 80 something volts is a bit low.

When you changed the 220k and 820ohm you have changed the gain formula of the tube..it will lower the gain some..but you will still have plenty of gain. Yeah just play it and see how it goes. Its hard to say on the hiss or noise..you can try many different tubes,and you will find some have alot less hiss sound..and also the EL84s can have little pops and ro crackles.. Mostly from old tubes..or dirty tube pins or sockets..since your amp is new parts,it very unlikely your having any of this..and probably just lead dress..or maybe a cold solder joint..these can all cause these problems..

Richie

[KingCrimson]

Yeah just play it and see how it goes. Its hard to say on the hiss or noise..you can try many different tubes,and you will find some have alot less hiss sound..and also the EL84s can have little pops and ro crackles.. Mostly from old tubes..or dirty tube pins or sockets..since your amp is new parts,it very unlikely your having any of this..and probably just lead dress..or maybe a cold solder joint..these can all cause these problems..
Richie

But again, this sound only comes from the TMB side. It's kind of like when you put on an old 78 from back in the 40s - that crackly sound, but very faint. But it also has this bassy hum kind of thing going on to an extent, but that's mainly when the MV gets above 5 or 6. When the TMB side is set to sane levels, everything is really fine. I just want the whole spectrum usable

What stones on the TMB side can I start turning over besides the resistors I've been jacking with as mentioned above? What about putting a grid resistor on the TMB input pin on V1? I'm gonna go ahead and try it for the heck of it. What about new pots that are the plastic conductive type?

Why is the TMB side always so moody? I guess all the fire it has boiling underneath tends to make it a bit wacky. Or maybe just in the hands of amp building pupae such as myself, inconsistencies come with the territory.