Tsl 100 help

[tomg666]

Hi,

I bought a secondhand marshall tsl100 ages ago its 1998 so not exactly reliable.

ive had to do work on it in the past so i have all the schematics and its a hassle but i love the sound settings and versatility.

two questions

mainly at the moment its started doing something very weird which i haven't heard anyone else complain about. You can play for about 10-15 minutes after warming it up and all of a sudden it will burst into a high pitched screaming noise for about 10 15 seconds. it changes in pitch varying and sounds very robotic and jumpy not like a smooth natural sound and it will keep doing this. Its the same sound everytime, following the same pattern. It has nothing to do with the guitar or lead. Also its nothing to do with its environment and interference as this happens in different places. This is not a faint noise its over powering and very loud. it is also definitely not the noise from a mobile phone before someone thinks thats it. There are no other side effects volume is the same, valves arent burning up, no burning smells or smoke, tones still the same no fluctuations in volume.



and secondly what changes would you generally advise to try and make it more reliable.

cheers for all input anyone has

tom

[oc disorder]

I'll attemt to answer ..well its breaking into oscillation intermittantly
this can be caused by a poor ground/earth somewhere or a faulty solder joint.
Can be a bit nerve wracking especially as it can happen at full power !
Somehow the output is creeping back into the input causing feedback.
For starters I would clean all the connectors with de-oxit or similar
then check over all the solder connections.
For testing I would fit some spare almost trashy output valves and with
an insulated probe tap around the connectors and where you have previously
repaired.I usually put an attenuator on the output (have an old Tom Sholtz power soak ideal for this) so I dont go deaf...!
Hope thats a start..

[mykey]

Hi,

I bought a secondhand marshall tsl100 ages ago its 1998 so not exactly reliable.

ive had to do work on it in the past so i have all the schematics and its a hassle but i love the sound settings and versatility.

two questions

mainly at the moment its started doing something very weird which i haven't heard anyone else complain about. You can play for about 10-15 minutes after warming it up and all of a sudden it will burst into a high pitched screaming noise for about 10 15 seconds. it changes in pitch varying and sounds very robotic and jumpy not like a smooth natural sound and it will keep doing this. Its the same sound everytime, following the same pattern. It has nothing to do with the guitar or lead. Also its nothing to do with its environment and interference as this happens in different places. This is not a faint noise its over powering and very loud. it is also definitely not the noise from a mobile phone before someone thinks thats it. There are no other side effects volume is the same, valves arent burning up, no burning smells or smoke, tones still the same no fluctuations in volume.



and secondly what changes would you generally advise to try and make it more reliable.

cheers for all input anyone has

tom

sounds like a bad solder connection, resolder the whole thing and try it again.

[tomg666]

ill take it apart and look at the joints but it doesnt sound like a bad joint as in i can give it a few good thumps and the only noise it gives out is the sound of the reverb tank. i checked over and redid all the bad joints last time it was in pieces. ive been trying to see if i can force it to happen which i cant it happens at low and high volumes and on all channels even when its not being played. making the same noise but it only seems to happen in maybe the first 5 or 10 minutes after it turning on. after its done it once or twice it runs absolutely fine.

could it be a failing capacitor between the stages? thats a guess but ill take another look and check the connections and look at the grounding.

cheers

[mykey]

Hi,

I bought a secondhand marshall tsl100 ages ago its 1998 so not exactly reliable.

ive had to do work on it in the past so i have all the schematics and its a hassle but i love the sound settings and versatility.

two questions

mainly at the moment its started doing something very weird which i haven't heard anyone else complain about. You can play for about 10-15 minutes after warming it up and all of a sudden it will burst into a high pitched screaming noise for about 10 15 seconds. it changes in pitch varying and sounds very robotic and jumpy not like a smooth natural sound and it will keep doing this. Its the same sound everytime, following the same pattern. It has nothing to do with the guitar or lead. Also its nothing to do with its environment and interference as this happens in different places. This is not a faint noise its over powering and very loud. it is also definitely not the noise from a mobile phone before someone thinks thats it. There are no other side effects volume is the same, valves arent burning up, no burning smells or smoke, tones still the same no fluctuations in volume.



and secondly what changes would you generally advise to try and make it more reliable.

cheers for all input anyone has

tom

If you have a bad solder joint LOOKING won't help you at all.
when the amp is on it heats up, then something is failing because of thermal
reasons. you can't see a thermal failing solder joint so that's a waste.
when the amp is on and warmed up TAP at each solder joint with a wood stick (chopstick) lightly to see if you can narrow down the location.
resolder ALL the joints in the amp regardless of whether they LOOK
bad or not. THAT's an effective way to solve a bad solder joint.
I would try replacing ALL the tubes or trading the tubes out one at a time, that's another good start. A tube could be going bad for thermal reasons.
another reason is a thermal failure in a transistor, after the transistor heats up it craps out. sometimes we use freeze spray (buy at electronics supply)
to cool each transistor slowly one at a time, then narrowing down the bad one.
if none of the above solves it, take it to the service center. it can take a lot of experience to solve a thermal intermittent problem, and intermittents are the hardest to solve. even the most experienced techs can have a hard time solving a thermal intermittent.
Clue: never assume anything! just because a solder connection LOOKS good does not mean that it IS good. just because a tube is new, or that it checks good on a tube tester does not mean that it IS good. These tests do not take into account THERMAL expansion. here is a link to a schematic for future references:
http://www.drtube.com/schematics/mar...tl10-60-02.pdf