Is the Marshall TSL 122 combo unreliable?

[MartyStrat54]

I was busy yesterday when I posted the above info. I did want to tell you that there is more to this installation. Most importantly you will need some rubber washers that go between the grille and the fan. This will isolate the fan unit and prevent excessive "whine" from the fan. I use four, 8/32 type bolts. These are small enough in diameter to go through the holes in the Marshall grille without any drilling. Put the head on the outside and the nut and lock washer on the inside.

You will need to drill a small hole in the bottom of the chassis. You will have to have the chassis pulled to determine where you can make the drill hole. It is best to make the hole oversized and then install a rubber grommet in it. Then you can pass the power cable through this hole over to the power switch. One wire will go to ground and the other goes to the "ON" switch. Make sure it is the right connection. You want the fan to come on when the switch is turned on.

I usually use stranded 16 gauge wire and that is plenty big for this application. I try to use just the right length of wire so that the excess just hangs without touching anything. (Attaching the wire to the grille may transfer fan noise.

Most of these fans have bare soldering terminals. You will want to use heat shrink tubing on these connections to prevent any possible shock from occurring. There may be some other little tweaks I do, but that depends on the individual amp. Sometimes I try different rubber washers to get the quietest mount. If your fan is below 35dB, that is really good and quiet. Let me know if you tackle the job. Just remember, these type of fans now come with a noise listing. Any fan of the proper size will do, just pay attention to the noise rating.

On a side note: If you had all four tubes replaced with YJ's, the heat problem would be a lot less than with EL34's in place. I notice that the YJ's have quite a long base to them and of course the EL84 is a much smaller tube and therefore it puts out a lot less heat. I do not think you would even need a fan if you were running a quad of YJ's with EL84's.

Marty

 

[Webslinger]

I did want to tell you that there is more to this installation.

I figured there was, thanks for adding the details. I was also considering some sort of cooling fan, myself and have some other questions and ideas on this.

Have you done an A - B comparison with a thermometer? With and without the fan? Just how effective in heat reduction would this be?

Evacuating the heat from inside the combo's case can be compared to an older full-size PC tower. There was usually an "entrance vent" of about 8sq inches, and there was the cooling fan mounted in front of similar sized exhaust vent. So inside airflow would follow a specific path, expelling heat through the fan while drawing-in cool air thorugh the intake.

Ok now what would happen is that people would (for any number of reasons) remove several of the rear expansion-card slot-covers, and/or leave the side access cover loose or off completely. What would happen was that even though the fan was running, the processor would still overheat. Why? Because of all the open areas, the fan was no longer baffled and just cavitating, and the "flow" of air was not moving from the intake to the exhaust port. (and this is why newer PC cooling fans are now mounted directly over the processor, with a duct-shroud. )

So anyway, I can see this same principle applying to a guitar amp.
I'll agree its probably better than having no fan at all, ...and your installation instructions are good & solid. But Im wondering.. with an open back amp (or even with the vented-solid-vented panels), Im not sure a PC fan (or similar electronics cooling fan) mounted the way you describe doing a whole lot..... unless it was a fairly good size, lets say at least a 4" blade fan? But then returns the question of Db level... not to mention any small RF field-hum from the motor that the amp might pick up. I know some amps already have a cooling fan, but I havent had a chance to look at one close enough to see how they have it designed as far as airflow.

Maybe a small cooling fan mounted to blow cool air directly AT the tubes might be better? Maybe with it's own battery for anyone who's unsure about tapping into the 120v (or 240v) onboard power?

 

[DragonSarc]

Like a beautiful girl, some Marshall amps just feel special when you are bending a G string through them...and others don't.

lolz hahaha

question: doesnt the tube has to be hot to sound good? putting a fan to cool it down wont affect the sound?

 

[joshuaaewallen]

lolz hahaha

question: doesnt the tube has to be hot to sound good? putting a fan to cool it down wont affect the sound?

Anyone here please correct me if I am wrong, but...

Basically just like a car tends to break down when it's a 100 degrees out, heat is also the enemy of electronics.

My understanding has always been that the tubes basically have filaments to heat them to where they should be temperature-wise for optimal operation, thus the glow, plus w/ the juice flowing throw them if they are working biased properly, and just plain working right, the tube temp isn't the issue. It's what the heat from all those tubes lined up inside the amp can eventually do to harm the other electronic components inside the amp that be be the problem...

That being said, if I am wrong about this anyone here please feel free to correct me.

 

[MartyStrat54]

That's 100 per cent right. In my hardcore gigging days, I played many an outdoor show with the temperature looming in the low 50's. The tubes are working just fine in this weather. Correct? So, cooling your tubes with room temperature air is not going to take them down to meat locker levels. All electronics have an upper and lower temp range that they can work in. I don't think Jim Marshall thought someone would try playing one of his amps after it sat out all night in minus 10 degree weather. You have to be realistic. The same for the hot side and playing in Phoenix and it is 115 degrees outside. We had fans on everything and you could hear it through the P.A. You ever hear of something called "thermal runaway?"

Conclusion: It's not so much taking heat off of your tubes as it is the buildup of heat on the chassis. A fan (four-inch BTW) mounted as I have described will cut the temp on the chassis. (In my old Peavey Mace with six, 6L6GC's, I had a really cool fan mod and I also installed a giant heat sink with thermal paste and rivets to the chassis. Of course I was in the Air Force and had access to all sorts of parts.) Anyway, a fan mod is not going to alter the sound of your tubes.

It's also nice to know that I have modern computer equipment, as I have a fan mounted on top of my processor (HP a350n with special Pentium 4 processor and 3G of RAM and a HP dv5000 laptop). Wouldn't know what to do without them.

And guy's here's another tidbit. There are some really quiet personal fans on the market. Take one of those and place it behind the amp. If you're not recording, it will do the trick and you don't have to do anything to your amp. I do things to my amp, because I can't help myself. I like the one-of-a-kind amps. I took the black grille cloth off of my 602's and put Marshall cane grilles on them with gold Marshall logo's. (Let me tell you that cane material is a PITA to work with.)

Well you are all a great bunch of guys and I really like this forum.

Marty

MUSICIAN'S AUDIO EQUIPMENT-MAKERS OF VERSACAB

 

[joshuaaewallen]

Funny then!! my TSL is the only one that has been reliable since 2003??? I dunno I guess I'm lucky.
I've rehearsed and gigged it and is just the best amp I have ever owned...
Cheers

Diddo... Mine was made in '99, and is a two owner amp. The bloke who hd it before me bought it new, gigged and recorded with it w/ no trouble. I am owner #2 and granted I really don't play out, it has given me no problems either.

 

[Kirk5443]

Any company that engineers an amp with a suppression cap in the output stage that is barely rated to survive in that circuit(500pv cap rated at 500v)is total bs that is a fine example of designed engineering for failure cause when that cap shorts it takes your tubes and possibly your output tranny.being a repair tech I have seen it happen 7 out of 10 times its ridiculous I will not buy any modern Marshall made ever again

 

[Webslinger]

Ok, here's some questions, but you are the guy to ask...

cooling your tubes with room temperature air is not going to take them down to meat locker levels.

I can understand, trying to cool with already hot outside or room temp may not make sense. But the output of any fan drops the temp by at least 10-15 degrees, so isnt that better than nothing?

playing in Phoenix and it is 115 degrees outside. We had fans on everything and you could hear it through the P.A.

Did you hear the fans buzzing being picked-up by the mics? Or was it an a hum caused by the electro-magnetic field, of a fan's motors.
And if so, would that be from being too close to an amp/PA, or a 60cycle feedback through the house power circuit, if the fan is plugged into the same outlet or powerstrip?

You ever hear of something called "thermal runaway?"

I heard of it but not exacty sure what it is.

It's not so much taking heat off of your tubes as it is the buildup of heat on the chassis. A fan (four-inch BTW) mounted as I have described will cut the temp on the chassis. It's also nice to know that I have modern computer equipment, as I have a fan mounted on top of my processor.

So if you were to install a 4" fan in an amp, whats the best way to do it;
A- place the fan to blow air directly onto the the tubes & chassis?
or
B- place the fan to blow outward, evacuating heat by pulling cool air through the case, as is done in a computer tower. Although Im not sure this would work very well with an open-back amp. You' probabaly have to seal the back, then install an "inlet vent" opposette the fan. This might end up being hotter than just leaving the back open?

And then whats the best way to power the fan?
Isolated batteries?
Splice into the AC power wire before the transfomer?
Splice into the DC output past the transformer?
And do any of the amps circiut chassis have some sort of auxillary power connection, that a fan could utilize (like on a computer's motherboard?)

I probably wouldnt do this myself, I take it to a tech, but Im curious?

 

[craigbeal]

I've got a 2004 TSL122 which I have had from new...

Played 100's of gigs with it now (7 years worth of road use) and never ever had a problem with it! No valves replaced, no services, no dodgy foot switch.. nothing!

Wonder if mine had a newer version main board however?

 

[bludolph1]

Hi, i had the same problems as most poeple with this amp and it has cost quite a lot of money in repairs/valves/fuses, the main problem always seemed to be that it over heats very qickley-buzzes and bangs! KNOW WHAT I MEAN
Sounds incredibly obvious but after two years of trouble i decided to put a standard desk fan 30cm away on low speed and guess what, no more problems.please try- i am at the moment touching wood as i have probably just cursed myselfFan obviously facing towards the back panel

 

[sidvicious]

i haven't cranked my tsl head in several years.

is the fuse you mention the small one? just over half an inch or so? if so, mine blew all the time and the amp was mint when i got it. after several replacements i shelved it. all of the tubes had been checked, and were in top shape.

so i said to hell with it. its still on the shelf.

this is my experience.

 

[Kid Klash]

Adding vents to the top of the cab (like the DSL100 and TSL100 heads) should help with the heat problem too : http://www.marshallforum.com/cabinets-speakers/65947-tsl122-combo-cab-mod-added-heat-vents.html

 

[Michaelprout]

I have the tsl 100 head and the 122 combo.i play in a metal band so they get hammered.my only issue was the board for the presence knob,reverb,fx mix had a solder joint for a ground wire that came lose making the controls work occasionally,now that was the head,easy fix!now the combo had the presence on the same board go out so I replaced that trim pot.now I brought them to my amp tech and apparently there is a resistor or diode that's used in the power section that if it burns out will destroy your power section.it is not needed.it was carried over from the jcm900 which did need it.it can be clipped out and then you eliminate that danger.symptoms start with a blown fuse.clipped mine out 2 years ago and I gig with them every weekend!i love this amp!im buying another head for a backup this weekend!i have no reliability issues with these!

 

[wallythacker]

Wait. what about this resistor or diode that "if it burns out will destroy your power section". I thought when a carbon resistor self destructs it goes OPEN. Meaning that's the same thing as clipping it out of the circuit.

Could you provide a diagram to show which component you clipped out to protect your power section?

 

[ntrueman]

There is a lot of people reporting issues with overheating and tube cooking or burning smells with this TSL 122 combo. The problem is the main board where the pcb breaks down and also wrong resistors fitted which causes bias instability issues. Change the main board and everything settles down, mine went from a smoking fire hazzard to purring tiger in approx. 1 hour. Order board here: https://www.tubesandmore.com/products/pcb-marshall-valve-pcb-tsl100tsl122

 

[Kiko]

Hey there MartyStrat54! Thank for your input on the fan. Mind if I pick your brain a bit more on the subject? I would like to know if you have any specific suggestions on:

1. What fan might be the best fan to select for this purpose?

2. How best to mount the fan (ie. in the metal grill on the back of the amp? Top? Bottom? Side? Etc.)

3. Can this be done utilizing the amps power supply, or would it be better to give the fan it's own, entirely separate power supply?

Any suggestions, and especially illustrations and pictures, are most appreciated!

I have posted this before somewhere here:

I use a small external fan to blow air at the back of the amp, i find this effective at keeping the components cool. It is very hot and humid here in Manila and sometimes I use my Tsl100 head in an non-air conditioned room, the fan keeps things cool.

 

[jason_s]

I bought my TSL122 new in 2004 and dealt with the bias issues and multiple trips to the shop. I opted for the the stable bias kit from Dr. Tube in lieu of the new board. For the most part it took care of the bias issues. After the repair I put in NOS preamp tubes and CP Svetlana EL34's. I biased it in at 80mV and it held solid for about 4 months before the bias started to drift high. It got to the point once the amp was warmed up I couldn't get it below 90-100. I replaced the tubes with a set of JJ 6CA7's and the bias dialed back in. I'm thinking about installing a head vent in the top of the cabinet to let the heat out. Don't know if the heat caused the tubes to go or if it's just the nature of CP tubes.

 

[Jethro Rocker]

Not that it matters to OP as this thread is nearly 10 years old but....
I used mine exclusively for nearly 10 years and 5 were before I knew what biasing was. Had no issues at all. Great sounding amp, one of my favorites. A 2001. Kept bias at around 90mV per side as per Marshall then dropped it to 84 ish. If issue is heat, I agree with the fan idea.