Need Help With Studio 22 Tune-Up

[suntower]

First post. Please be gentle.

I have a 1990-ish Caliber .22 Studio I haven't touched in about a year. In almost-new condition.

So I plug it in yesterday and it has magically developed the following symptoms:
1. A noticeable hum
2. VERY weak volume
3. Reverb not working
4. When I push or pull a bit on various knobs (yes I know they aren't meant for this), the volume and tone magically re-appear for an instant.

I was thinking that, since there are no obvious bangs/bruises, my buddy suggested that it probably just needs new tubes and/or filter caps. Does that sound about right? If so, I'd like to try to do this myself. So...

1. Do these symptoms comport with old tubes/filter caps? IOW: is there a reasonable chance that this will 'fix' everything? (Including reverb?)

2. Is this a job for a 'pro' or can I DIY? (I -used- to fix TVS 35 years ago but haven't touched a soldering iron in 20.)

3. Do I need to replace filter caps? How much do they cost? How hard are they to install? (ie. simple desolder/resolder new ones?)

4. How much are new tubes? Do I need to buy a complete new set or just the power ones? Where to obtain?

5. My only (minor) grouse was that the amp never seemed to have a 'full' enough tone. It was great for rock/crunch/rnb but I seem to recall it being a bit 'thin' for full jazz chords. Assuming I can do the work, is there something (cheap) I can do to help with this?

THANKS!

---JC

 

[MichaelC4]

my buddy suggested that it probably just needs new tubes

Your buddy is probably right.
The most part, maybe 95% of Mesa amp problems are tube related.
Sounds like your tubes are worn out.
Your amp takes 2 EL84 power tubes and 5 12AX7 preamp tubes.
Here is the cheapest I could find on eBay. - http://www.ebay.com/itm/Tube-Complement-for-Mesa-Boogie-Studio-22-/121432475078?hash=item1c45f085c6:g:ntYAAOSwGvhUD1~x

When I push or pull a bit on various knobs (yes I know they aren't meant for this), the volume and tone magically re-appear for an instant.

Clean out all your potentiometers (pots).
Clean out all your input and output jacks.
Check out YouTube videos if you don't know how.

Your reverb is located inside the chassis.
I have the bigger 6L6 brother, called the 50 Caliber.
I looked inside at my reverb and a braided wire had come loose and needed to be resoldered.
Plus, the month and year that your amp was made will be written in there.

Hope some of that helps,
Mike

 

[suntower]

Thanks. Sorry for the slow reply. A couple of follow up questions:

1. Is there a difference in tube quality? ie. I saw that eBay advert, but I've also seen other companies offering sets that are literally 200% more expensive.

2. I disassembled the top and the pots are of the sealed back variety. There's no place to put cleaner as in the old days. Is it still possible to clean? If so, how?

3. Didn't see =any= broken or loose connections on the inside. I did notice that replacing the filter caps will not be easy. Can't figure out how to remove the circuit board. How is this done?

4. I didn't see =any= internal markings indicating the date of manufacture. But the inscribed number on the chassis is SS1770. Can that be used to indicate when it was made?

TIA,

---JC

my buddy suggested that it probably just needs new tubes

Your buddy is probably right.
The most part, maybe 95% of Mesa amp problems are tube related.
Sounds like your tubes are worn out.
Your amp takes 2 EL84 power tubes and 5 12AX7 preamp tubes.
Here is the cheapest I could find on eBay. - http://www.ebay.com/itm/Tube-Complement-for-Mesa-Boogie-Studio-22-/121432475078?hash=item1c45f085c6:g:ntYAAOSwGvhUD1~x

When I push or pull a bit on various knobs (yes I know they aren't meant for this), the volume and tone magically re-appear for an instant.

Clean out all your potentiometers (pots).
Clean out all your input and output jacks.
Check out YouTube videos if you don't know how.

Your reverb is located inside the chassis.
I have the bigger 6L6 brother, called the 50 Caliber.
I looked inside at my reverb and a braided wire had come loose and needed to be resoldered.
Plus, the month and year that your amp was made will be written in there.

Hope some of that helps,
Mike

 

[Don]

You might be able to desolder the caps from the top without removing the PCB and install the new caps on top of the board.

Clean the effects loop jacks. They cause big problems with these amps when they're dirty.

The pots in my '89 Studio .22+ could be cleaned by spraying Deoxit in the gap between the solder lugs and the housing. Your pots aren't like that?

 

[MichaelC4]

Sorry for the slow reply.

That gives time for someone, that has had the same problem or knows more than myself, to chime in.

1 Yes. Some brands are better, to some people, as far as dependability quality.
And some offer different grades of performance quality. Mainly in preamp tubes.
Such as, I currently have 4 different grade Shuguang 12AX7 tubes, ranging from less than $10 each to $35 each. 12AX7, 12AX7B, 7025 and 12AX7-T
Power tubes don't have much variant, but, if you ever order power tubes for a MESA, make sure they are listed for MESA or tell the seller you need power tubes for a MESA. They are specific to the amp, bias wise.

2 The opening is on the side of the PCB board. I heated up the end of a little red spray tube to make a J hook and was able to get contact cleaner up in there. (edit- oops I was thinking of a solid state Marshall for some reason)

3 I can not speak about caps. I have never messed with them. That is usually a last resort type of move.

4 The first time I look in my Studio Preamp, I didn't see it.
It wasn't written in the same place as my 50Cal.
Look for some black marker.
10/90 was inside the Studio Pre on the PCB.
6/90 for my .50Caliber+ on the metal of the chassis.
I have yet to open up my Racktifier, Quad Preamp and 295 Power Amp.
I think MESA/Boogie has records on the serial # and dates.

 

[MichaelC4]

Not to make things too confusing, but both my amps I looked in just have month and year.

 

[Don]

You might be able to desolder the caps from the top without removing the PCB and install the new caps on top of the board.

Looking more closely at my amp, I don't know if my previous advice to remove the filter caps from the top is possible (I've done this with small components). The existing filter caps are a tight fit. I've had the PCB partially out on mine. If I recall, I pinched the end of the plastic standoffs and they released from the holes. It's been a while.

 

[suntower]

Hello all... THANKS FOR THE HELP! An update.

When I disassembled the unit, I basically just cleared out the dust and wiped everything clean. After I re-assembled the unit?

GOOD NEWS: No hum! And the thing appears to mostly 'work'. The volume seems a -teeny- weak, but not terrible. It may actually be within spec. Woohoo!

BAD NEWS:
1. However, the reverb still doesn't work. What's weird is that I can hear the spring 'thunder'. IOW: When I shake the thing I hear the amplified spring ringing. BUT... the signal from the guitar is totally dry. It's as if the reverb return is being summed back to the power stage, but no guitar signal from the pre-amp is getting to the reverb pot.

2. The pots are still noisy. But I will open it up again and look to see if there is an opening in the pots on the sides where I can spray de-oxit.

SO QUESTIONS:

1. Any ideas on how to fix the reverb? I didn't notice any broken wires.

2. Can I assume that replacing the tubes with a cheap-o set will restore any loss in volume? I've had this amp for 25 years so I assume so, right?

3. Can I assume that the filter caps need not be messed with?

Any further assistance would be MOST appreciated!

---JC

 

[Don]

I've had an amp's reverb do that because of a bad cable. Could be the tank as well.

You can try cleaning the tube sockets. I remove the tube, spray a little deoxit on the tube's pins and put the tube back in and wiggle it around.

If they're original tubes you'll probably benefit from replacing them.

 

[MichaelC4]

I've had this amp for 25 years

If they're original tubes you'll probably benefit from replacing them.

+1

Might even bring your reverb back.
On the .50Caliber+ one of the 5 preamp tubes is the reverb tube.

 

[suntower]

Hi if anyone is still watching this topic -and- has a .22 I have some questions and I need a favour.

I cleaned everything, then swapped the tubes and re-soldered 2 obviously broken connections on the back of the PC. The hum went away and the volume is fine. YIPPEEE!

So everything seems to be working now EXCEPT for the Reverb. If you hit the amp, you hear the 'thunder'. The springs are definitely amplified. But the signal is not going through it. I can't see any obvious broken connections.

QUESTION: Can someone post a piccie of the circuit board (when you take it out of the cabinet)?

QUESTION: Is it possible that -one- of the tubes is busted? Can I simply swap the 5 small tubes (12AX7s?) and see if that's the trouble. IOW: are the tube portions of the circuiit like the EQ wired in parallel so that I can -hear- if that's the trouble. Or is there another easy way to check. I have a circuit diagram, but I can't always be sure which solder points on the backside correlate with the diagram.

Any help would be MUCH appreciated.

TIA,

---JC

 

[suntower]

Nobody?

 

[OryCheyne]

Hi, lucky you have a 22, probably going to be awesome once you've finished with the tune-up
I've received my share of help from this forum it's a great source of information.
The manual states valve position 4 is the reverb tube. Just replace that one if I were you, this may fix reverb. Apologies but I can't load photos, using my Windows phone, bit painful.
If you want also change the two el-84 power tubes and compare how it sounds. Those other preamp tubes may still be sweet depending on how much you played them way back.

http://mesaboogie.com/media/User Manuals/Studio_22_manual.pdf
You should be able to get spray into the pots by removing the knobs and spraying a little at the base of the stem then operating the pot to work it in. Try this with the amp on so you can hear when it's clean.
Get a very short 1/4 inch 1/4 inch jack and leave the effects loop permanently bridged. (Effects out to effects in), just works in avoiding random volume loss and. Scratchy crap.

I had probs with my reverb, one of the really thin wires to those really small wound transformers at the end of the reverb springs was completely off. I thought it needed to be replaced but an excellent tech seemed to solve the problem without replacing it. Wish I knew what he did to fix it. My little 22 is really beat up but with the geq can really sound special.

Good luck

 

[Don]

So everything seems to be working now EXCEPT for the Reverb. If you hit the amp, you hear the 'thunder'. The springs are definitely amplified. But the signal is not going through it. I can't see any obvious broken connections.

This indicates that there is still output from the reverb tank but no input. Check the tube first (you can swap them with each other, though, if you have a bad tube, it might cause a problem somewhere else in the amp). If that doesn't help it's usually a connection or the tank itself. Rough handling can cause damage to the delicate wires inside.

 

[suntower]

Right. Please look at top photo. I swapped tubes. No difference.

I noticed this white wire, which -seems- to be connected to the shared ground wires along the rear jacks.

Anyhoo, I tried connecting it to the one open connection on the reverb and again it made no difference.

I see the -very- tiny green/purple pairs of wires that go to both sides of the reverb tank and they seem intact.

1. Where does the white wire solder to? Is it significant?

2. If that's not the issue, does this photo show anything else suspicious?

TIA,

---JC

So everything seems to be working now EXCEPT for the Reverb. If you hit the amp, you hear the 'thunder'. The springs are definitely amplified. But the signal is not going through it. I can't see any obvious broken connections.

This indicates that there is still output from the reverb tank but no input. Check the tube first (you can swap them with each other, though, if you have a bad tube, it might cause a problem somewhere else in the amp). If that doesn't help it's usually a connection or the tank itself. Rough handling can cause damage to the delicate wires inside.

 

[Don]

That white wire looks like it should be connected to that tab on the reverb tank as a ground. Don't take my word for it though- my .22+ had a traditional separate tank so it was a different setup.

 

[McBarry]

Hi,
my Studio .22 repair shots are on a HDD in dead PC = sorry no help there as yet..
Chasing lost signal is relatively easy.
Check continuity with DMM from the input RCA PLUG through to the isolation coil - the little fella with the green/black leads to it.
Check the one at other end of tank also. It's conducting, evidenced by your thump test, but it might be close to fail also.

If all intact, work backwards - from the jack on pcb backwards.
BUT my money is on a mechanical failure in a lead or of the tiny tiny conductor wires in the tanks transformers.
I've fixed many where the TINY conductor wire has fractured right after the connection terminal joining the green/black lead. Be warned, U need magnifying glass and a cool soldering iron.

Re white lead - looks to go to the earth rail on the chassis sockets. If so, seems to want to go to the earth lug on the tank in your pic.

Dave