[ 'Dead CRATE BV- need help! ]

[g1]

Slightly confused about it being 'almost never fail here'

No one said that!!! You (incorrectly) reported that it was 0 ohms (shorted). THAT is what we said was rare, a shorted resistor. Here is what was said:

For a resistor to fail to a short or zero ohm condition would be very rare.

I have NEVER seen a shorted resistor.

So, while a shorted resistor here would be very rare, an OPEN resistor here is not uncommon.

Btw will a generic Maplin (the common UK component 'leccy store' High Street place) 5w wirewound be ok.. or do you suggest a Ohmite/ s'thing specifically GTR tube-amp? and would a 7w 150hm be a better idea in lieu of the failure? a bit bigger but no prob really.

Any generic 150 ohm 5 or 7watt will be fine. It's not a new amp, so it's not like that resistor is failing all the time because it's only a 5 watt, it's probably lasted the life of the amp.
There may have been some fault at another point in the amp's life that stressed the resistor, who knows?
Just make sure to mount it the same way as the original, if it's off the board, keep the same spacing from the board.

[Sea Chief]

Sorry g-one! I got my 'shorted' & 'open circuit' wrong as the same thing that's all (another ditty Ive learnt then: shorted=zero ohms/ but open is not the same). I knew what I meant/ saw (a fkd R!) just my terminology was wrong thats all.

Now the max voltage I see on the generic 5w 150 Ohms wirewounds seem to be 200V or so. But there's over twice that V either side of R99?

Will a Welwyn W22 be v high voltage maybe? Ive seen these iirc as replacements in fenders (or new build fender circuits).

cheers SChief

[g1]

Open circuit is the opposite of short. Infinite ohms. Like when your meter leads aren't touching anything. You said your meter reads "I", for infinite. Many meters will read "OL" (open loop or over limit or overload).

The voltage rating for resistors is for the voltage across the resistor. In this case, the schematic shows about 2 volts (450V on one side, 448V on the other).
So the voltage rating is not a factor here. It would be a factor for a resistor that was going from a high voltage point to ground.

[Sea Chief]

Do you know what.. I understand all that (& previously yr point too that R99 cannot be cause of crunchy noise, due to obvious x&y in retrospect). I had thought that was actually a 1. on my MM. I think Ive learntmore here than 3 yrs of high school physics tbh!

Noted the placing of the R99 above board too- looks a good few mm's.

Ok excite! now, I have tantalisingly right here (it'll take another week to get the 150 Ohm 5w) two 7w wirewound 100 Ohms here in my bitsbox.. and one 'Wellwyn W22' enamel 7w 270R. What do you think? (single 100, or parralel to get 185?). Probably daft.

thanks g-one.

[Sea Chief]

Ok amp is running again.. but with the goddam crunchy noise again! sheesh what to think now..

Fwiw I joined a 7w 47r + 100r for the 150 ohm. A few Ohms off should be ok?

[Jazz P Bass]

The resistors in series is o/k.

Is the crunchy noise on both the Clean & Lead channels?
Does the noise go away when you put the volume/ gain controls to zero?

Now may be the time to plug the guitar into the FX Return jack.
The preamp gets bypassed in this configuration.

[Sea Chief]

The resistors in series is o/k.

Is the crunchy noise on both the Clean & Lead channels?
Does the noise go away when you put the volume/ gain controls to zero?

.

Noise on both channels JazzP. Noise does -not- go away with vol/ gain to zero.

[Sea Chief]

[Did a few cap chnges between C16 > MV. No difference/ bad crunchy noise firmly there. Now a quite big pop switching between channels- maybe as at the mo Q4 is reversed 'cowgirl' but works, tracks bad so has to stay as is for now].

Im ready to try the FX thing. Hasnt the prob been established to b4 the MV though? the fat R only just recently failed (only ~ reply #168/ corresponding to that 'lovely' vv quiet I found, around C16/ Q4/ C17 tinkering). I guess going back a firm step maybe needed tho. Understood if so.

many thx SC

[g1]

I think it would be best to reset and start over. Forget about the other thread, there were some inconsistencies that did not make sense. A fresh start may catch something that was overlooked.

You said the gain/vol controls did not affect the noise. How about the master when switched to ch.2, any change?

The FX return jack splits up the preamp from the power amp. It is a very convenient place to divide the amp. Plug into the FX return jack. Does the noise remain or does it cease?

[Sea Chief]

Yes a fresh start would be most welcome. A clean pair of heels.

Vol and Gain (ie ch2 vol) are at 0 always.. turning either up & noise is unnafected/ resolutely there. GTR heard tho ok behind this mess of noise.

MV is at MAX always (ch2).. turning MV down to 0: noise ceases to quiet.

GTR into FX rtn: noise ceases/ quiet.

[g1]

Jumper from V2 pin2 to ground, is noise there or not (master back up).

[Sea Chief]

hi g-one.

V2 pin2 to gnd, MV up.. crunchy noise ceases, but loud 'durrrr' hum instead (diminishes with MV turned down/ quiet at 0).

thx SC

[g1]

Try jumper from V1 pin7 to ground.

[Sea Chief]

Try jumper from V1 pin7 to ground.

Done: [edit] V loud hum/ 'durr'. I cant tell if crunchy noise behind.

[g1]

Jumper from C3/C4 junction to ground.