Mesa Quad Re-cap ??

[jreiser]

Hi,

Finally got some time to give my quad some tlc, I’ve just given it a re-valve but I’m still having some problems. There is a high pitched noise when certain controls are turned up high on LD2. I’ve had a good read of previous posts and it seems a re-cap may be in order.
If so which capacitors need to be replaced, I’m happy to do the work myself but I just need a little guidance.

Any help would be greatly appreciated......

 

[TemporarilyStairs]

Can't actually help with the re-cap, though I'm curious since my Quad is acting up and I think it's likely the caps as well. I did want to mention though that as far as I'm aware the high-pitched squeal/feedback/screechy thing might actually be normal: it's actually even mentioned in the manual, in the context of the Lead Bright being pulled. I've personally noticed it even when the Quad was functioning properly, but only at pretty extreme settings. Don't know how much of it is a design quirk and how much of it can be avoided/worked around, but figured that was at least worth mentioning; it might still be worthwhile to recap the thing though, of course

...NOTE: At high gain settings, especially in Lead 2, the Lead Bright
control may cause excessive squealing and pickup feedback. To avoid this annoyance when high
gain and high volume settings are in use, push in the Lead Bright. If this is undesirable, either the
Lead Drive or the Volume must be reduced.

 

[Whoopysnorp]

I recently recapped my Studio .22 (well, with the exception of one cap for which I didn't have the correct value), and it was a huge improvement. You'll want to replace all the electrolytic caps, principally the big blue ones (those are the power supply filter caps). You can probably find the schematic online; I found the schematic for my Studio Preamp with ease. The electrolytic caps are the ones with a polarity indication on the schematic. The orange ones are coupling caps and do not need replacing.

Bottom line is be VERY careful with the power supply caps; they may hold a lethal voltage. Make sure you have a voltmeter that can read up to 500VDC, and be sure to check the amount of charge in the caps. If it measures anything over 10 volts, you'll need to drain them with a resistor (recommended 25Kohm 10W cement-type). When you are checking the voltage or draining the caps, keep one hand well away from the circuit (this is to attempt to ensure that if you do get shocked, the current won't travel through both arms and your heart), and wear safety goggles! I got lucky and my caps only had a couple of volts in them, so it was a fairly easy job that I'm glad I did.

 

[daveyboogie]

Just in the process of servicing my Quad this week... I ordered four new 30uF 500V, two new 220uF 350V and two new 220uF 63V caps made by F&T in Germany, not the original Mesa and Sprague type caps that were in there but the F&Ts are supposed to be sweet (and they're not cheap). I'll let you know how it works out. I'm also changing the LDRs and orange drops associated with Lead 1 cos I've got some other issues with this channel. By the way, the PSU filter caps for the Quad don't appear to be on the schematics- at least not the schematics I've got.

 

[ak47]

Just in the process of servicing my Quad this week... I ordered four new 30uF 500V, two new 220uF 350V and two new 220uF 63V caps made by F&T in Germany, not the original Mesa and Sprague type caps that were in there but the F&Ts are supposed to be sweet (and they're not cheap). I'll let you know how it works out. I'm also changing the LDRs and orange drops associated with Lead 1 cos I've got some other issues with this channel. By the way, the PSU filter caps for the Quad don't appear to be on the schematics- at least not the schematics I've got.

Let us know how it turns out... should be interesting!

To Whoopysnorp... 'shockingly' good info there.. nothing worse than a bunch of angry volts shooting up the arm! :twisted:

 

[Whoopysnorp]

Just in the process of servicing my Quad this week... I ordered four new 30uF 500V, two new 220uF 350V and two new 220uF 63V caps made by F&T in Germany, not the original Mesa and Sprague type caps that were in there but the F&Ts are supposed to be sweet (and they're not cheap). I'll let you know how it works out. I'm also changing the LDRs and orange drops associated with Lead 1 cos I've got some other issues with this channel. By the way, the PSU filter caps for the Quad don't appear to be on the schematics- at least not the schematics I've got.

Let us know how it turns out... should be interesting!

To Whoopysnorp... 'shockingly' good info there.. nothing worse than a bunch of angry volts shooting up the arm! :twisted:

Is that a Strategy 500 I see in your avatar or a Simul 395? I have the 395 with the Studio Preamp and wow...what a rig. I can't imagine the sheer brutal volume that close to 200 watts per side would generate...

 

[ak47]

It is a Strategy 500... and yes, this amp fills space like you wouldn't believe because it still stays musical even when pushed...

The cleans are '4-dimensional' and the dirt tends to want to keep on going like when you accelerate in a sports car... I can make snare drums curl up and wimper! :twisted: I rarely take it beyond level 4 though.

I must say that a class A switch would be the icing on the cake... the 395 is an awesome beast!

 

[jreiser]

Great advice guys, thankyou...

Im going to order the caps in the next couple of days, and i think im going to replace the LDRs at the same time just to cover all my bases. In terms of draining the caps first, first class point. Ill never forget getting shocked from one the first time....Havent done that since..... :lol:

Ill let you know how it pans out.

Regards

Joe

 

[RonS]

Hai, I read your posting about recapping MB Quad and am wondering how it turned out. Was it a succes?

Today I retubed my Quad with 8 JJ ECC83S. Sound has improved on all wordking channels. But after one minute Lead 1 stopped en I couldn't repair it. Even with the old tubes it doesn't work. Before the retube channel 2 (volumechannel) was a lot softer then channel 1.

I think my quad needs a recap too, that's why I would like to know how succesfull your's was.

Thanks, Ron

 

[daveyboogie]

Either LDR-11 or LDR-13 but first check plate voltage through 82K resistor to pin1 of V23 (315Vdc ish). Mine was blown when I first powered it up.
Does the volume for Lead-1 intermittently rise and fall and then disappear alltogether? If so, more likely LDR problem. If Lead-1 is completely dead then the problem is probably plate resistor. Please be carefull if checking voltage on resistor pins:- probably best to check first with power off with resistance meter check across resistor. If resistor is blown open circuit it is possible to piggy-back a new resistor onto the old resistor's legs.

Re-cap is probably not worth it IMHO. Replacing LDRs made biggest difference to tone in my Quad.

HTH.

 

[RonS]

Thanks, managed to fix the lead1 problem with a new resistor.

How can new LDR's make such a great difference, as they are only for switching purposes?

Regards, Ron

 

[daveyboogie]

Glad you fixed Lead-1.

At least one LDR in my Quad was totally dead; possibly the LED wasn't emitting or the LDR had broken down or something. Another LDR was intermittent and when I replaced it the tone on R1/L1 came up brighter, cleaner and much less noisy. Not sure what caused them to fail in the first place... Possibly my dodgy 110V to 220V conversion!

 

[Friedmett]

My Quad is a 220 voltage version.

When using the FU2 board all lights are on on the board and Quad. It used to work fine but why I have no idea. When the FU2 is unplugged the Quad works fine.

I'm going through a Marshall 2104 combo which has an added effects loop. Somehow the A channel output is getting lower and lower while the B is fine.

It sounds great though. I have had the rising and falling volume but its been a long while since I heard it.

I opend it up and saw the tubes were Grove tubes.

Any ideas on what is wrong with my Quad?

 

[ak47]

My Quad is a 220 voltage version.

When using the FU2 board all lights are on on the board and Quad. It used to work fine but why I have no idea. When the FU2 is unplugged the Quad works fine.

I'm going through a Marshall 2104 combo which has an added effects loop. Somehow the A channel output is getting lower and lower while the B is fine.

It sounds great though. I have had the rising and falling volume but its been a long while since I heard it.

I opend it up and saw the tubes were Grove tubes.

Any ideas on what is wrong with my Quad?

Might be a bit obvious... but is the FU-2 plugged into the correct jack? If it is dark back there you may be running it into the Abacus input by mistake...

Alternately, it is most probably the cable shorting out I think. Make a new one yourself and it will not cost you the fortune of ordering a replacement one. Even if it is not the cable, it is always good to have a spare.

Does your Marshall have the volume problem without the Quad running? Might be an idea to check your Quad through another dedicated power amp if you can... Do you run the Quad in 'mono' through your Marshall (as this is not a stereo amp...)? Remember, for mono operation of the Quad, take your choice of output jacks and turn the other to zero.

This may fix the A/B level problem you mentioned but knowing your signal chain will tell us more.

 

[Friedmett]

The signal chain is simple.

Guitar to the input of the Quad.

Quad Channel B main out to effects loop return on the Marshall. The Channel A does not work well connected the same.

The Marshall works great otherwise on it's own. When connected this way the Marshall is bypassed and I only use the poweramp section with the Quad handling the preamp.

This gives a good blend of old Marshall(1978) with 25 watt Celestions speakers and Mesa/Boogie gain. It does not sound like the Marshall has a big effect on the tone as I have tried a Marshall stereo poweramp once. That did not sound to good.

I run in "mono" as I do not have a Boogie poweramp yet. Being in Denmark there are not many around.

The FU-2 can only be connected one way at both ends so it must be the cable.

 

[ak47]

The signal chain is simple.

Guitar to the input of the Quad.

Quad Channel B main out to effects loop return on the Marshall. The Channel A does not work well connected the same.

The Marshall works great otherwise on it's own. When connected this way the Marshall is bypassed and I only use the poweramp section with the Quad handling the preamp.

This gives a good blend of old Marshall(1978) with 25 watt Celestions speakers and Mesa/Boogie gain. It does not sound like the Marshall has a big effect on the tone as I have tried a Marshall stereo poweramp once. That did not sound to good.

I run in "mono" as I do not have a Boogie poweramp yet. Being in Denmark there are not many around.

The FU-2 can only be connected one way at both ends so it must be the cable.

How does Channel A not work the same? If you compare levels and it is a small difference in volume at the same setting, this is normal and varies a bit between Quads.

 

[Friedmett]

The signal chain is simple.

Guitar to the input of the Quad.

Quad Channel B main out to effects loop return on the Marshall. The Channel A does not work well connected the same.

The Marshall works great otherwise on it's own. When connected this way the Marshall is bypassed and I only use the poweramp section with the Quad handling the preamp.

This gives a good blend of old Marshall(1978) with 25 watt Celestions speakers and Mesa/Boogie gain. It does not sound like the Marshall has a big effect on the tone as I have tried a Marshall stereo poweramp once. That did not sound to good.

I run in "mono" as I do not have a Boogie poweramp yet. Being in Denmark there are not many around.

The FU-2 can only be connected one way at both ends so it must be the cable.

How does Channel A not work the same? If you compare levels and it is a small difference in volume at the same setting, this is normal and varies a bit between Quads.

I've just tested it and Channel A is very very low even on 10 compared to Channel B.

 

[ak47]

Try swapping the V22 tube as it handles the outputs and FX return (Second from the right as you look from the back of the Quad) and see if it helps.

Alternately, you could just run the FX send straight into your Marshall... you may even prefer the sound of this over using the A + B outputs!

 

[Darth Bacelar]

Bump!

I know that I'll probably sound sooooo noobie, but...

I saw those abbreviations around the site, but what means LDR, and cap?

 

[Jackie]

Bump!

I know that I'll probably sound sooooo noobie, but...

I saw those abbreviations around the site, but what means LDR, and cap?

LDR - [L]ight [D]ependent [R]esistor

Cap - [Cap]acitor :wink: