Marshall TSL 100 head turns on but tubes don't fire up

[PaulReedMarshall]

Guys,

I've got a TSL 100 head that turns on but I get no sound out of any channel. I've replaced all the fuses (hoping it was the mains fuse). None of the old fuses were blown. But replaced them anyway. None of the tubes fire up. Meaning I turn it on for 10 - 20 minutes and no glow.

Is this a tube problem? Or a power supply problem? Any ideas are welcome!

Thanks

 

[PaulReedMarshall]

Oh and I've tried different guitars, checked cables, different speaker cabs etc.

 

[clydey]

can you read a schematic and do you have a multimeter and are you comfortable working on the inside with the power on.do you know how to discharge the filter caps
the reason i am asking is that it looks like some live testing may be needed after you have metered out the heater section and the fault may be better determined by a competent tech
cheers

 

[PaulReedMarshall]

Thanks for the response Clyde. Yes, I have a multimeter, can read schematics and have no problem working on it hot / live. Don't know how to discharge the filter caps... yet. But I'm searching now or you could tell me how. So, what do you recommend I start with? Any ideas?

Oh, and I've been to guitar center to ask about repairs. The shop that they send their Marshall repairs to no longer works on Marshalls. So I looked at the Marshall site... the one they listed doesn't work on them any more either. In short, if it's something I can do I'd like to give it a shot cause my next option is to pay shipping to a shop out of town / state. That is, unless someone on here knows a shop that works on Marshalls in the Memphis, TN area.

 

[clydey]

ok take out the 4 power valves and switch on tha amp.
does the preamp valves light. if so one or more of your power tubes has shorted
try that first

 

[PaulReedMarshall]

I'm at the office right now. So I'll try that as soon as I get home. Any other ideas you can shoot at me between now and the next 3 hours would be greatly appreciated. I will post results as soon as I do this.

 

[clydey]

ok get the schems from schematic heaven or drtube
download a data sheet for el34 to familiarise yourself with the pins layout
i am assuming that the primary of the transformer has power and that the main fuse is ok
basically the ac heater voltage to the pins of 2 and 7 (4*el34) comes from the mains transformer secondary (in parallel) and each return leg is individually fused therefore a short in any valve should in effect blow that fuse (all slow blow 6.3) this voltage is then bridge rectified and sent to the preamp heaters
therefore concentrate on the heaters for the power tubes as it looks like this heater voltage is not getting through
also if you look at the transformer heater secondary there is a couple of resistors worth checking(these are the first 2 after the transformer heater secondary on the schematic)
what i would do is
take the power lead out of the wall
discharge the caps (see jon wilders posts)
check for continuity from one end of the transformer heater secondary through each valve and its associated fuse back to the other end of the heater secondary.
check for continuity of the heater secondary transformer windings
live test check for 12 volts ac on pins 2 and 7 of each power valve (if not there test across transformer heater secondary
it could also be the bridge rectifier( feeds the preamp tube heaters)pulling the heater voltage down (this bridge rectifier can be checked with your meter or unsoldered to see if the heaters are restored to your power tubes
i would suspect the tranformer secondary heater windings last of all.
hope this helps and hopefully some of the more experienced techs will pitch in
cheers

 

[PaulReedMarshall]

Excellent info Clyde. I've got the schematics and will start on all of this as soon as I get to the house. And if anyone else has some ideas to add to all of this I certainly will appreciate it.

Thanks again

 

[MartyStrat54]

Wow! You mean no one works on Marshall's in Memphis. WTF? What do they work on...Fenders?

Don't know how old the tubes are, or if they are the originals, but a bad preamp tube can knock the signal out. However, if you are saying that the "heaters" are not coming on, then that sounds like a power supply problem. Do any of the tubes glow, such as an orange glow inside the tube? If not, then you will have to get into the chassis. Remember, it's your decision to work on this amp. You proceed at your own risk. The TSL has approximately 475VDC when turned on. Touch the wrong thing and arc welding could occur. It is not a very easy amp to work on, especially for a beginner.

Here is the schematic showing the distribution of 6.3V to the filaments.

http://www.drtube.com/schematics/marshall/tl10-60-02.pdf

Right off of the power tranny, check W9 and W10. The readings will be in AC. If good, follow the schematic and check F1, F2, F3 and F4. Then the circuit goes to V4. Check pin sockets 4, 5 and 9. Put black on 9 and touch 4 and 5. Check the same on V3. See special note on V2 and V1. The power tube should read 6.3V and the ECC83/12AX7's should read approximately 12.6V. (6.3 plus 6.3)

One other important note. Set your meter to DC Volts when checking V1 and V2. These tubes use DC voltage on the heaters to reduce hum. The other heaters are AC, so set your meter accordingly.

Also, tubes socket pin numbers are counted from the bottom of the socket going in a CW direction. Looking at them from the top, you start on the right side of the gap on the 12AX7s and count CCW. You should be able to check the 6.3V on the Power tubes from the F1 through F4 test points. The pins used are 2 and 7 on the EL34's. So on the right side of the index pin count CCW to locate them. If you have a solid DMM, I would set the voltage on "AUTO," because if you touch the wrong place and its 475VDC it could ruin your meter.

If your 6.3V and 12.6V are okay, then it is time to consider shipping the amp.

 

[clydey]

excellent but thought el34 heaters 2 and 7 (6.3v yes)
i was thinking of the ecc83 twin triode feed (12v dc ie rectified)in this case
been a long day
cheers

 

[MartyStrat54]

Well I am going to agree that it is pins 2 and 7, but did you look at the schematic? To me it seems like it says pins 2 and 6. I know pin 6 isn't used in an EL34, so 7 has to be it. Just another brain fart.

 

[jcmjmp]

Well I am going to agree that it is pins 2 and 7, but did you look at the schematic? To me it seems like it says pins 2 and 6. I know pin 6 isn't used in an EL34, so 7 has to be it.

The JCM2000 pin numbers on the schematics are not the usual tube pin numbering so be careful when look at the schematic. The pins only refer to the PCB, not the tube socket.

 

[clydey]

yes but noticed it before and just put it down to a misprint
cheers

 

[PaulReedMarshall]

Marty, yeah it's the craziest thing huh? I can't find anyone around Memphis that actually works on them. Everyone I've talked to says they would ship it off. Guitar Center won't even do that. They told me to call a company, I did, that company doesn't work on them anymore... It's weird being in a pretty big musical hot spot and no one works on Marshall?

Clyde, pulled the power tubes (EL 34's and yes they are the originals so yeah they are old) and the preamp tubes still don't fire up. Keep in mind, that my problem is none of them are firing up...

I read another post somewhere that said to plug into the receive fx loop to see if any signal comes out... tried that. No sound.

I also saw another post about pulling the preamp tubes and putting them back in one at a time. Has anyone tried that? Can someone walk me through that?

Everyone, thanks for all the info. I've got the schematic that Marty posted the link to. I'll start running through everything you guys mentioned and will post what I find.

Thanks again

 

[clydey]

Marty, yeah it's the craziest thing huh? I can't find anyone around Memphis that actually works on them. Everyone I've talked to says they would ship it off. Guitar Center won't even do that. They told me to call a company, I did, that company doesn't work on them anymore... It's weird being in a pretty big musical hot spot and no one works on Marshall?

Clyde, pulled the power tubes (EL 34's and yes they are the originals so yeah they are old) and the preamp tubes still don't fire up. Keep in mind, that my problem is none of them are firing up...

I read another post somewhere that said to plug into the receive fx loop to see if any signal comes out... tried that. No sound.

I also saw another post about pulling the preamp tubes and putting them back in one at a time. Has anyone tried that? Can someone walk me through that?

Everyone, thanks for all the info. I've got the schematic that Marty posted the link to. I'll start running through everything you guys mentioned and will post what I find.

Thanks again

pulling the power tubes was only to eliminate the possibility of a power tube pulling the heater line down without taking the associated fuse.
you will get no sound until your heaters are working. the receive loop only tests the output section which will not function until the heaters are on.
also check across each individual heater pins of each output tube (out of circuit) for continuity/resistance pins 2 and 7 just in case a fault has caused the heater filament to open
just to clarify the output tubes are parallel wired
this means that filament/associated fuse/circuit continuity/and ac voltage on the tx heater secondary/2 hold off resistors at tx heater winding/ no shorts/ bridge rectifier ok(feeds the preamp heater windings)
if all above ok then that particular output tube should glow even if the other three output tubes have filaments open
if you have voltage across the sec heater winding tx then you are halfway there
hope this helps cheers

 

[PaulReedMarshall]

Great info everyone! I've got my kids this weekend. So probably won't get to work on this until Monday. I'll run through everything that you have all recommended and post results. Thanks again to everyone!

 

[PaulReedMarshall]

Guys, I started down the list that Marty posted.

"Right off of the power tranny, check W9 and W10:
W 9 checks at 124
W 10 checks at 446

"If good, follow the schematic and check F1, F2, F3 and F4."

I get no readings off of these. So, um, next step?

By the way, thanks again guys!

 

[Jonathan Wilder]

Guys, I started down the list that Marty posted.

"Right off of the power tranny, check W9 and W10:
W 9 checks at 124
W 10 checks at 446

"If good, follow the schematic and check F1, F2, F3 and F4."

I get no readings off of these. So, um, next step?

By the way, thanks again guys!

Those numbers don't look right. Make sure the meter is set to VAC, not VDC. Don't measure from both terminals to ground. Measure ACROSS the terminals right off the transformer (one probe on W9 and the other probe on W10. Should only have one reading and the reading should be somewhere in the neighborhood of 6.7VAC with no valves installed.

If no reading, disconnect the wires from W9 and W10 and read them right off the transformer. If still no reading, the heater winding in the power transformer is dead and you'll have to replace the PT.

If it comes down to replacing the PT, I can get you a good deal on a Mercury Magnetics upgrade PT.

 

[PaulReedMarshall]

Thanks Jon, they didn't look right to me either. But while I was waiting to see if anyone would respond, I was looking through all the connections and found a couple that were really loose. I pushed them all tight and fired up the amp. Now all the tubes are firing up. But, I don't want to consider this "fixed" just yet. Let me close up the amp and fire it up, play, power down, repeat a couple times. I'll let you all know how it goes.

 

[clydey]

i think its fixed
sorry i didnt respond earlier
me and martystrat54 had a seperate date and couldnt respond right away
but glad its fixed
cheers