DSL 50 Not Working

[aspguitars]

When I checked the tube pins on the board as you say, I probably did it wrong. When I looked at the tube sockets, they are numbered. However I don't think this represents the pin numbers. If I was to look at the tube from the bottom, can I presume that starting on the left of the gap they are numbered clockwise. I found this site for a similar tube. Vacuum Tube Pinouts
Obviously looking at the solder joints on the board I've got it back to front. Even so, the figures still don't look right. I also did the measurements with the tubes in situ for continuity which I hope was correct.

 

[Melodyman]

Take it to the shop..

 

[scat7s]

label and remove your wires from the standby switch, and test for continuity on that switch/

bleed your filter caps first.

sorry about the fuse thing, i just wasnt clear that you had verfied the ht. as long as the mains fuse is intact, it will power up whether or not the ht is ok.

let me know how your standby sw tests. be sure to make a little sketch and label the wires so you can be sure to put it back where they belong.

also, i noticed on your other thread, you have replaced the power trans. are you certain you have wired it correctly? double check that as well.

get back when you can....

 

[scat7s]

Take it to the shop..

thats beginning to sound like the best option....

 

[aspguitars]

Hi! again Scat7s,
I've just done some more pinout checks, and quess what.
Unbelievable!

Although very low readings on most of the pins, now getting 454v DC on pin 5 and 441v DC on pin 6.
V7 is almost identical. I removed and replaced the main circuit board to check some other components, so could be a dry joint or similar that I've disturbed.
AC readings very low on both Tubes.
Still no output though!
Another guy on here recommended that I change the output transformer which I had. Not the power transformer. I took a photo of the cables first to avoid wrong connections, and I've checked on here with another pic so I'm sure thats OK.

 

[RickyLee]

Hi! again. I've had a look at the Marshall Circuit Diagram, and it's not very clear. I can't see where the power valves get there DC supply from unless they are acting as rectifier valves. (not sure about this)
It looks to me like Pins 2 & 6 are the Heater Pins, 1(G3), 4(G2) & 5(G1) are Grids and pin 3 goes to W4 on the output transformer. Can I presume that this is where I get the plate voltage?
It's really hard unless you know where to test. There are no test points on these diagrams which is not much help.
Any help would be muchly appreciated.
Ade

Be careful with that schematic drawing, as there is a typo on there as well as the TSL100 schematic has the same typo as well. The typo has the power valve EL34 pin numbers wrong.

The typo is they are showing pin 8 as pin 7 and on the two heater filament connections, they should be pins 2 & 7 and they show pin 7 as pin 6.

And also take note that there is a 2001 revision as well. Check to see which year you have there.

 

[scat7s]

Hi! again Scat7s,
I've just done some more pinout checks, and quess what.
Unbelievable!

Although very low readings on most of the pins, now getting 454v DC on pin 5 and 441v DC on pin 6.
V7 is almost identical. I removed and replaced the main circuit board to check some other components, so could be a dry joint or similar that I've disturbed.
AC readings very low on both Tubes.
Still no output though!
Another guy on here recommended that I change the output transformer which I had. Not the power transformer. I took a photo of the cables first to avoid wrong connections, and I've checked on here with another pic so I'm sure thats OK.

sounds to me more like you didnt have a good connection to ground when you took your readings the first time.

find some bare metal, or a clip right to the ground lug on the chassis.

ok, so thats good news....so lets try this again.

retake all your readings at all the pins and let us know what you find. all in DC, except 2 and 7 should be AC, 6.3v + or - (2 and 7 are taken together, one probe on each pin simultaniously, you do not connect to chassis ground for the AC heater check.)

also, taking into account what ricky has mentioned, dont rely on the schematic for your pin orientation. use the keyway in the tube socket as your physical landmark. and pull up a datasheet like i suggested before to help you.

 

[aspguitars]

Hi!
I think you could be right about the connection problem
I've enclosed a pic of the EL34 Spec Sheet. You can see the problem that I'm having with the pinout. The spec sheet does not specify whether the pin numbers are from the top or underneath. It looks to me as if I am looking at the tube from the bottom. So what to me would be pin 1, is in fact pin 5 (g1)
pin 3 looks like the plate (anode), but they don't seem to go in a logical sequence to me. See what you think. I'll wait for your reply before I take the readings.
Ade
http://www.drtube.com/datasheets/el34-jj2003.pdf

 

[scat7s]

ok, i see whats messing you up.

locate the "key". the tube can only fit into the socket one way, due to this keyway. see it?

ok, now, making note of where that key is from the underside view, (in case it is not visible) if the key is oriented on "top" of your view, (12 oclock), then the first pin clockwise is 1, all the way to 8, in order clockwise.

i think you mentioned it above, but i didnt confirm, b/c i didnt have socket in front of me and i couldnt remember if it was cw or ccw..., sorry...

to confirm that your orientation is correct, you should see 450vdc +/- on pins 3 and 4, -30vdc on pin 5, and no appreciable dc voltage on the other pins, however, red probe on pin 2, and black probe on 7 simultaniously, at AC setting on the meter should show you your heater voltage. (6.3vac)

with power OFF, check continuity to chassis ground via pin 8 and pin 1.

post up results from all of these pins please. make it easy to read, start a new line, skip a line, whatever....

 

[aspguitars]

Readings as requested. V7 not included as almost identical. Hope this is legible this time

V6
Pin 1 0.01v DC
Pin 1 1v AC

Pin 2 0v DC
Pin 2 3v AC

Pin 3 458v DC
Pin 3 1.7v AC

Pin 4 448v DC
Pin 4 0.18v AC

Pin 5 -31.5v DC
Pin 5 0.02v AC

Pin 7 0.0v DC
Pin 7 3.0v AC

Pin 8 0v DC
Pin 8 ov AC

between pins 2 and 7 5.9v AC on V6 and 6.02v AC on V7

Continuity between pin 8 and 1 to ground good on both V6 and V7

 

[scat7s]

cool, that all looks pretty good.

next thing is to check continuity between chassis ground, and the sleeve of your speaker output jack. please be very specific as to exactly how many ohms you see here, or 10ths of ohms as the case may be...

have you tried plugging your guitar straight into the loop return as suggested in the other thread?

 

[aspguitars]

Hi! again, sorry for the delay, but have been really busy. I've just measured for continuity on all 3 output sockets.
16 Ohm Socket = 0.4R
Both 4/8 Ohm Sockets = No continuity at all!
Can I presume this is not good?

 

[scat7s]

nope, not good.

what speaker jack have you been using?

you need to hardwire a ground to the sleeve tabs of the 4/8 ohm jack(s)

take it right off the 16 ohm. this is common on the DSL.

there are threads on this forum that can help you with a couple different approaches to do this mod. search it out.
JCMJMP was one of the original posters in one of them i beleieve, that might help you locate it using the advanced search function.

ok, next: have you plugged your guitar into the loop return yet?

 

[aspguitars]

Hi! again. The latest results.

I plugged my guitar into the return socket of the effects loop on the back as suggested, and again got nothing on the 4/8 Ohm outputs. When I plugged into the 16 Ohm output I'm getting sound, but not good and crackly! is the best way to describe it.
I then plugged back into the 4/8 Ohm output and gave it a temporary negative (Ground) with another lead and still no sound.
So, when plugged into either the front jack input or rear loop return, I get sound on the 16 Ohm socket, but nothing on the 4/8 Ohm sockets.

I hope this is clear enough

Thanks
Ade

 

[scat7s]

yeah, but dont try to run from the 4/8 jacks again until you get them modded/repaired. thats bad for your OT.

ok, so we have sound, but its crackly sounding? is that right? well, you said that your bias was waaaaayy low right? check it again, verify exactly what you have for your bias right now, and if its still low, try to bring it into range. i know youve already done this, but im trying to work this thru in a methodical manner so that we can feel confident that we've kind of given it a full, comprehensive checkup.

also, i forget, did you say those are new power tubes or old ones that came with the amplifier? if they are in any way, "unknown" as far as their age, use, current condition, you need to buy yourself a new set of power tubes, rebais and see what youve got for bias current/voltage.

if you get a new set of tubes, and still have bias issues, we can correct the issues, and you'll have a nice set of spare power tubes when the time comes to change them. being a tube amp owner, you should have some known good spares (pre and power) around for troubleshooting and repairs anyway. so dont worry, even if you dont need them right now, they wont go to waste, and now that we can feel ok that your voltages are pretty well in spec and all that jazz, we need to eliminate possible power tube failure b4 we start chasing other stuff....low bias can indicate a power tube that is at the end of its useful life.

i also want to stress DO NOT use the 8/4 ohm jacks until they are repaired. that can ruin not only your power tubes, but your output trans. your better off mismatching an 8 ohm cab using the 16 ohm jack for a short time, then running no load, NEVER do that.

 

[scat7s]

here is the link for the speaker jack mod

http://www.marshallforum.com/workbench/24249-marshall-jcm2000-speaker-jack-ground-mod.html

 

[aspguitars]

Hi! again and thanks for the link to the socket mod. I'll do it anyway, but surely if that was the problem, when I gave the 4/8 Ohm socket another ground (negative) with a test lead it should have worked?

 

[scat7s]

well, i suppose it depends on how you did it. and if you did it in a way that created a clean path to ground.

did you use alligator clips?

 

[aspguitars]

Hi! again,
it doesn't really matter now anyway. I did the underboard output socket mod just now by linking all the grounds on the sockets together. It is still the same. 16 Ohm socket very crackly, both other sockets, nothing at all.
Where to next lol?

I'm just hoping that the fault has not taken out the new tubes that I put in!

 

[scat7s]

ok, give me a few to look over the schematic.

meantime, measure your sleeve to chassis ground on the 4 and 8. continuity in the following manner

plug in a cable, and measure from the sleeve of the end that is not plugged in (the end that would go into the cab jack) to chassis ground.



and let me know what you get.


also, do you have some lube/contact cleaner?