Lots of noise, changed caps, no bueno

[Chris5150]

@5150 Can measure a voltage for me? ON the tubeboard you see 2 resistors mounted horizontally, both are 10k (Brown Black Orange Gold) measure on the right side (red lead of the meter) of one of them (black lead of the meter to ground or chassis) , you should have +- 190V. Let me know.

Hey man, sorry it took so long for me to get around to this. I am measuring 174-176V at both the brown black orange gold resistor.

Also, I turned the gains all the way up, and started going up on the master volume, nothing in the input, and this high pitched whistle shows up at around 7.5 -8 and gets progressively louder until the EQ clip light comes on bright. Then when going down on the master volume on the initial step down, the whistle gets higher in pitch and fainter, then goes back to it on the next step. The whistle goes away once you hit 7. When you max the EQ it is much worse.

[Chris5150]

I measure 214 VAC at the tube board connector to the transformer, then 174-176 VDC at the resistors.

[MarshallJMP]

Did you measure this at the left side of the resistor? You need to measure on the right side of the resistor.

[Chris5150]

Did you measure this at the left side of the resistor? You need to measure on the right side of the resistor.

Yes, my apologies, it was the wrong side. Now testing the correct side the resistors measure 188-189V.

Have you ever experience a high pitched whistle with one of these things? I'm starting to wonder if it's an op amp. Thanks!

[MarshallJMP]

There are 3 shielded wires coming from the tube board to the main board, try to move them around, see if that does anything with the whistle. Use a wooden pencil just to make sure you won't get zapped by touching something on the tubeboard !!

[Iperfungus]

Uhm...it reminds me in some way of a similar issue with my MP1 after mods (but mine also has a MDRT transformer inside)...
I really pissed of poor MJMP a lot about it...sorry mate....


Have a look here: http://adadepot.com/index.php?topic=1992.135

I ended to fix the issue by placing an external buffer between guitar and MP1's Input...that's something you can try, if you have any buffered pedal (any Boss, for instance...just put it there, the buffer is alway active...), so I didn't mind about it anymore.
But it would be interesting to see if it's the same issue on your side and if it will finish to have a different and common solution.  :banana-skipping-rope-smiley-e

@rnolan: hey hombre! News from MikeB? Are you guys doing all right?

[rnolan]

Hey Max  , this does seem similar to the issues you were having, not sure if it's quite the same  :dunno: .
Mike and I are ok, both still have our jobs. Triple whammy here in Oz, years of drought, worst fires ever (we were blanketed in smoke over xmas/new year) and now the virus...  Last I spoke with Mike he was getting a new kitchen (with all that entails).  Going into winter here, getting very cold.  How's things in Italy? you guys copped a huge battering from the virus...

[Iperfungus]

Hey Max  , this does seem similar to the issues you were having, not sure if it's quite the same  :dunno: .
Mike and I are ok, both still have our jobs. Triple whammy here in Oz, years of drought, worst fires ever (we were blanketed in smoke over xmas/new year) and now the virus...  Last I spoke with Mike he was getting a new kitchen (with all that entails).  Going into winter here, getting very cold.  How's things in Italy? you guys copped a huge battering from the virus...

Yep.
Such issues can make you go crazy. Slight differences, from case to case.

The only one, as far as I remember, having the exact same problem as me, same MP1 and same mods was MikeB...maybe, after the kitchen's affair, he will run a test with external buffer? Or he's already done with that?  :lol: :lol: :lol:

Happy to see you're doing fine, guys.
I'm in touch with a friend from Melbourne and I was really astonished about fires in Australia and Siberia last year.
So sad...so crazy.
Now the COVID-19...no rest for Aussie people... :facepalm:

About Italy....our first problem is...the italians.
After almost 3 months of total lockdown, now everyone (not me) is going out everywhere like crazies.
I'm not sure if the government is fooling us to scare people or if people is stupid and we're risking a second and worst phase.
Very dangerous moment.
Nothing compares to USA and Brazil, but I wouldn't play with fire as people is doing here right now.

[Chris5150]

I finally had time to mess with it and taking a chop stick and applying pressure to the wire to the tube board changed the pitch of the high frequency whine. Applying a buffered effect (BOSS SD-1) did not help. It appears plugging in a guitar with the volume knob turned off introduced another whine of lower frequency while the high frequency whine gets worse but lowers in pitch a hair.

Edit: Thanks again for all your help and direction!

[Iperfungus]

I finally had time to mess with it and taking a chop stick and applying pressure to the wire to the tube board changed the pitch of the high frequency whine. Applying a buffered effect (BOSS SD-1) did not help. It appears plugging in a guitar with the volume knob turned off introduced another whine of lower frequency while the high frequency whine gets worse but lowers in pitch a hair.

Edit: Thanks again for all your help and direction!

Yup.
As Richard correctly predicted, looks like a different issue.  :dunno: