DSL50 Voltages

[dpm309]

Have a Marshall DSL50 that was having issues with cutting out and crackling with the tone shift button pressed in.  Grounded the 16ohm jack to the 4/8 ohm jack that took care of the cutting out problem.  Also replaced link 27 with a .047uf 600V cap that eliminated the crackling.  Played it a while with no issues.  When my bandmate played through it for about a 1/2 hour, he heard a pop and lost most of the volume. Checked the voltages:

Valve        Pin 1   Pin 2   Pin 3   Pin 4   Pin 5   Pin 6   Pin 7   Pin 8   Pin 9
V1 12AX7 256       0         1.8     *            *     194    0        1.4      *
V2 12AX7 277        0         2.3     *           *     303     0        2.9     *
V3 12AX7 402      241      244     *           *    241     0       1.6      *
V4 12AX7 283       25        41      *            *   289    24       40       *
V5 EL34    *         *           471  462       -37    *     *      0         *
V6 EL34    *         *          472  462         -38     *     *     0           *

I cannot find Marshall voltage chart for this amp anywhere. V3 looks off to me.  Is 400VDC normal for the plate voltage?  Any other ideas?

Thanks,
Dan

[sluckey]

Is 400VDC normal for the plate voltage?

It is for a cathode follower. Got a schematic?

[dpm309]

I believe so.  I have attached the schematic.   
Thanks,

[dpm309]

Using my amp stethoscope I traced the problem to the cap I added in place of Link 17. I added this cap to get rid of some scratchiness when the tone shift was pushed out as recommended by someone on another forum. Removed the cap and reconnected the link and it is working again. Not sure how this cap could have caused all of this as the amp worked perfectly until the effects loop was used.  I ran a couple of pedals in the effects loop and played for about 1/2 hour with no problems.  Will run it over the next couple of days to make sure it is working properly.

[shortfuse]

No 400 on the plates of a pre amp tube is not common at least not on that amp. V3 pin 1 and V2 pin 6 seem off.  Actually they all don't seem quite right from what i remember working on 2 this past year.  I can take voltages on mine and post if you need them.  Now that you have the link back in.  Deox the mode buttons I had the same problem on the green Chanel deoxed them pushed the buttons in and out several times rapidly been working fine for the past 6 months since.

[dpm309]

Apparently 400V is not uncommon for V3 since it is the cathode follower.  Found someone's voltages for the DSL50 and they are not that far off. Shortfuse, I would appreciate seeing your voltages to compare.  Been running it for about an 1 1/2 hr so far with no problems. Also thanks for the tip on cleaning the mode buttons.  I will give it a try.