My new..used Tube amp is always a warm distortion?

  • Thread starter Thread starter CoolCat
  • Start date Start date
this is a 40watt amp.
2005, Marshall 2000 DSL-401 (same board as the 201/20watt) combo 1x12.


I'm not sure how to check the B+?

I'll bet your right, in that there's something out of calibration that prevents from achieving 1.375V per the schematic.

I don't mind getting back into it though...it's always some learning and interest.:D
 
B+ is the high voltage line feeding the output tubes... check it at either the stand-by switch or the first filter cap... relative to ground of course...
 
resurrected form the Dead...Marshal 401

ok just to keep this post "focused".....

I now have a crap sound again.

I assume its the other tubes this time. However no orange glow or anything.

I pulled the 3 tubes "Marshall VALVE 00055" and WK42/05

I assume the WK42/05 means week 42, year 2005.

I assume these are the 3 preamp tubes.

I assume I can swap them out with something at Guitar Center?

I assume someone will respond and help ensure I don't tottally fhk up my amp!:eek:

:p.......and I'm off to the races
 
I have no personal experience with that amp but I was looking into buying one once but read many reviews online about how they got so incredibly hot it would melt internal components. I'm not really good with amps and pretty much all I can do by myself is change tubes. I wish I could help more.
 
Preamp tubes?

i think one of the obvious reasons this amp & board and electronics gets so hot is the tubes are upside down so the heat rises and the board absorbs it all, as the board is above the tubes.

any "upside down" design like this would be the same most likely..I'd think.


As far as the stock preamp tubes I have 3qty MARSHALL VALVE 00055?....I guess they are dual triodes and a 12ax7 will work fine in their place.
not sure why there are 3qty though....unless Clean, OD1, and OD2 are 3 separate channels?

Or they are ECC83S's..I keep seeing this tube mentioned too?


Edit #2

So I found another tube, 00063. It was underneath a silver cap/cover next to the transformer.

Is this a 12x7 type too? ECC83S?

any inputs appreciated!

back to info digging....




note- on biasing for the DSL401 from a different post
I tried following several documents for biasing this amp, one of them directly from Marshall. It will not reach the mV spec of 1.3-1.4mV. The highest it can be adjusted to is 1.01. The result was even lower when I tried a completely different set of tubes.
 
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COOLCAT said:
Or they are ECC83S's..I keep seeing this tube mentioned too? Is this a 12x7 type too? ECC83S?
Click to expand...

Yeah ECC83S is the same thing as 12AX7. Apparently, according to my dad, who used to work on electronics in the days when everything had tubes.

ECCS83S, I think is the european, or at least the English terminology for it.

As far as preamp tubes go, they, or at least the 12AX7's anyway (being the only tubes I have any experience of buying and installing thus far), are significantly cheaper than power amp tubes from what I can tell. It might be worth just buying a new set of those too.

I can understand your frustrations RE: maintenance however. I bought a Peavey 6505 a year ago, and it sounded like there was something seriously wrong with it, which I, through some chatting on here, ascertained was due to flunky preamp tubes. Strangely, it was only about 2 months ago that I managed to afford to get the money together to replace them (2007 was a hard year), and they only arrived at the beginning of this week. Retubed it a couple days ago. Now it sounds like a dream.

As you say, we all probably spend more on strings. It is well worth it to have a good tube amp, even if the maintenance is a little costly. And spending the extra money on getting a set of shiney new tubes will mean at the very least that your mind is at rest as far as tube maintenance goes for a few years. And if you still have the problem you are having now, at least you eliminated the possibility of it being the tubes.
 
picture showing the tubes and "odd" capped tube
 

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thanks Legionserial

I looked at the schematic on the link ...and all 4qty "preamp tubes" are ecc83 on the schematic.

however, physically I removed 3qty Marshall 00055 and the "odd" one -Marshall 00063 (silver cap)...

very strange to a amateur tube-smith:D



edit- found this little note to on someones post:
mine is re biased to 0.7 and has been going for 9 years !!!

as I understand it the lower/colder bias is set it adds clarity, the higher bias/hotter adds a bit more crunch/od?

headin' to GC for some tubes again...and will probably drop my bias back down, from the current maximum setting.

I guess v4 is a "phase inverter", (the "odd" one with a cap.)

but the schematic shows all ecc83...so I'll get 4 ECC83S's or 12ax7 what ever GC has.
 
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Just for your information Coolcat, I bought a TSL 601 second hand last summer and will be replacing the tubes in it really soon. I'll let you knwo how it goes.
 
i can't tell you what the marshall labelling (00055 and 00063) means. in fact, i'd bet that the people in china who put that amp together don't know. :D

but i CAN tell you that: ecc83 = 7025 = 12ax7.

as legionserial stated above, ecc83 is nothing more than the british designation for a 12ax7, so british amps that use the 12ax7 will have them labelled/indicated as ecc83. in american amps you will typically find them labelled as 12ax7 (or 7025 in old fender amps). they are the same tube.

it's kinda like how the brits call an elevator a "lift".....or the trunk of a car the "boot". but it's the same thing. :p

the silver cover is nothing more than a cover. it offers some protection.

so you've replaced the el84's but not the 12ax7's right? the 12ax7's typically have more of an effect on the amp's tone than the power tubes.

i bet that you've got either a dying preamp tube or two........or they're just crappy chinese tubes.

hate to say it, but it's time to replace those 12ax7's. i'd start with V1, which should be the one under the cover, and then work from there. they do NOT need to be matched, but you probably want ones with balanced triodes for the phase inverters (typically V3 and V4 and closest to the power tubes).

i know that replacing the tubes can be a lot of $$. that's why i'd recommend upping your initial investment and purchasing some New Old Stock tubes from someone like Mike at kcanostubes.com. they will FAR outperform and outlast the "modern" tubes being made today. i think a nice RCA Blackplate would do good things for that clean channel (V1).

that said, i've been researching what other folks have said about this amp and it seems that a good clean sound is NOT what this amp is about. so it's possible that if you want a completely clean sound, you're just not going to get it out of this amp.


cheers,
wade
 
COOLCAT said:
Damn thing got really, really hot on the gold face plate too....or maybe that was my "hot playing"...nah,,, :p it's a malfunction.
Click to expand...
didn't I tell you to put a fan on that thing?

I no longer run any of my amps without a fan on them.
I get these little 'squirrel-cage' fans from WalMart for $15 .... they work nice because they draw the air in from the sides and so don't get fouled on drapes or stuff behind the amp. It keeps the amp cool to the touch.
It occured to me that it was possible that tubes might need to be at some optimum operating temp and when I was talking to a tech at Mesa about something else, I asked about that and he didn't seem to feel it should make any difference so I keep a fan blowing directly on the power tubes and the back panel and have no heat problems at all ever.
 
COOLCAT said:
I guess v4 is a "phase inverter", (the "odd" one with a cap.)
.
Click to expand...

The phase inverter is going to be the one closest to the power tubes.

That one is closest to the input jack, it's going to be the first gain stage. It has the cap on to give a little protection against noise, since the first stage with the low-level guitar signal is the most vulnerable..:)
 
interesting. phase inverter..

yeah I have a full size fan and the back plates off mine....I was just at GC they have a bunch of ac connectors that allow a female double off the back of the 3-prong ac to have like a fan plug available I thought, $1.60.
The adaptors sitting there waiting with a demo pair of HR824 for $400 pair for me! dang they wanted $600 I offered $400 out the door and they siad they'd do it...US model too.....I may have to lay away.:confused: geez I just went in for tubes?

ok... all the original 2005 tubes are now replaced. whatever they were?

Installed 4qty 12ax7 (ECC83) Mesa Engineering PreAmp tubes STR-12-AX7-A. $45 schamolies... its all they had supposedly.

also put the 16ohm BlackGold in there as the Vintage 30 didn't do it for me. I guess the V30 is a bit darker someone posted...I don't know.

tuning the bias back down to .8V-.9V. now...... something doesn't seem right about the 1.35V bias setting on the schematic and then even at max it can't be reached?

sound right on the bias?

dementedchord asked to check some V+ or B+...I can do that now thats its opened up too.
 
ok set the bias at .886V on 1 to 2-com and 3 to 2-com.
The HT B+ voltage was 469V. taken off the standby switch (yellow to ground).

I guess no setup for the preamp tubes? Don't see any pots or anything.

Putting it back together.
 
all is well... hope to revive this thread in about 2-3yrs.

ah yes....now I can hear the reason I bought this thing.:)
 
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