Power Tranny Swap Problem - DR 100W 3ch MultiWatt

[WannaBoogie]

Hi again everyone.

This time a technical question. As some here already know, I am trying to swap out the stock power tranny (120V) to a Mercury Magnetics (100V). Of course, schematics are not made available for current production amps. So...

The problem is this:

the original Mesa tranny has 11 leads on the secondary.

the new MercMag tranny has 9 leads on the secondary. (According to Paul at MercMag. It IS the correct replacement)

The two extra wires on the original tranny are brown. And supply about 9.6-10V according to the technician. but, without schematics, we do not know what circuit it is supplying... or why

So, what are the brown leads for? and...
What are we supposed to do with the new tranny to properly connect it to this amp?

I do have a message in to MercMag. But, it is "off hours" there now. And, was thinking to hedge my bets if anyone has any knowledge about this.

Thanks

EDIT: BTW, the Mercury Magnetics P/N is MESAB-DUALR-P-120/240

 

[domct203]

I believe that 10V is the power supply for the switching matrix. You might need to tap power from the bias supply of the new tranny.

Paul & Patrick at Mercury are awesome, I'm sure you'll get the info you need, just 6 more hours to go until they are open.

We've got a few good techs here also, hopefully one will chime in sooner.

Dom

 

[WannaBoogie]

I believe that 10V is the power supply for the switching matrix. You might need to tap power from the bias supply of the new tranny.

Paul & Patrick at Mercury are awesome, I'm sure you'll get the info you need, just 6 more hours to go until they are open.

We've got a few good techs here also, hopefully one will chime in sooner.

Dom

Yea - Paul has been great! He got that tranny wound and out the door in <24hours...

The tech gave me a big smile and one of those "That's what I was thinking" looks when I told him about your suggestion. Of course, we will wait for confirmation from Mercury... and any other authoritative sources. ;-D But, if it all pans out, he should be able to finish it by Saturday eve, He did mention that extra parts would be needed. I just nod and say "whatever you need mate... whatever you need."

But, this is all Greek to me... Everything I know about analog electronics could fit in ole' Gram's thimble with space to spare.

 

[domct203]

Hey bro, read here starting with reply #4:

http://ampworkshop.yuku.com/topic/4793/Mercury-Magnetics-Mechanics#.TqAsb_15nTo

I think you need to apply the advise in reply #7, but the diode # is most likely different.

Hope this helps.

Dom

 

[WannaBoogie]

Hey bro, read here starting with reply #4:

http://ampworkshop.yuku.com/topic/4793/Mercury-Magnetics-Mechanics#.TqAsb_15nTo

I think you need to apply the advise in reply #7, but the diode # is most likely different.

Hope this helps.

Dom

Thanks man! That looks promising. But, it is pretty much Greek to me...

Are they saying that the two brown wires supply 5V each to the rectifier heaters OR 50V (2x25V??) to the switching circuit?

Is it possible to simply tap into the Bias lead and create two leads of the correct voltage from that (using the 220 Ohm resistor mentioned? or does it require the deeper surgery into the amp?

I'm sorry if these questions seem stupid. I'm just trying to get a grip on exactly what I should tell the tech... (In Japanese no less) Evidently Mesa Japan is even more unhelpful in this situation.

I contacted MercMag... No help. The reply was; "I have nobody here that I can ask about the wiring of the PT"

Cheers

 

[domct203]

I'm no tech, just making an educated guess. I would think that you should already have the rectifier tube filaments taken care of, you just need to get 10V to where the brown wires went. It seems (from the thread I linked) that you could follow the old Dual Recto schematic which should be available on the net.

Maybe try posting in the thread I linked? Hopefully one of the people in that conversation will reply.

Also, you could try contacting member "Monsta-Tone" here at the Boogie Board. I believe he is a Mesa Tech.

Good luck bro, if I find or think of anything I'll post ASAP.

Dom

 

[WannaBoogie]

Thanks Mate! I really appreciate all the help. It has gotten me tantalizingly close to the answer.

The quest for boogie continues....

 

[domct203]

I think I found the schematics that were referred to in that link. You can see the 50V blue (BLU) tap on the transformer in the Power Supply drawing, and again referenced at the 220 ohm (220R) resistor at the beginning of the switching matrix. Remember, these are not for your specific amp, your tech will need to deciede what value resistor to use for the correct voltage drop from 50V to the 10V you had from your OEM transformer. I hope this helps.

POWER SUPPLY:

SWITCHING MATRIX part 1

SWITCHING MATRIX part 2

Dom

 

[WannaBoogie]

Ok then... Here is where we are at this point...

The new DR (at least the revision I have) does indeed use the same power supply as the Triple Rec. The 11 secondary leads are all the same. (The rectifiers are connected in parallel) For the DR, the two extra leads (Brown and Brown) supply 14V@1A to "ACC". I'm assuming that is the aforementioned Switching Circuit(?).

The issue is that Mercury does not yet offer the Triple Rec PT in an "international" model (I needed the 100V tap) otherwise the TripleRec PT would have been perfect for this application. (Drop in replacement)

So, anyone who has the DR Reborn 3ch/Multiwatt MAY have the 9 lead PT or they might have the 11 lead PT, depending on production revision I guess.

For most folks (those using 120V or 220V primary taps), this is not an issue since both PT types are available with those taps. I screwed the pooch by needing the 100V tap.

Summary:
If you want to upgrade your DR Reborn's tranny... FIRST take a look to see if your original PT is 9 lead or 11 lead. If you can see Brown wires, then it is 11 lead.
If it is 11 Lead, Then the Mercury MESA-TRPL-REC-2CH-P what you need.
If it is a 9 lead, then the Mercury MESAB-DUALR-P-120/240 is what you need.
Both PTs supply the same specs on each secondary winding and color coding is the same.

For my solution, what we have decided to do is to install an independent PT rated for 12V@1A (14Vunloaded) to supply the voltage to those two connections. I think It is an acceptable, if not very elegant compromise. (And, it was suggested by Paul at MercMag)

OH! and also, if you under-power this circuit, it will create noticeable noise issues as we discovered by slowly ramping the voltage to the circuit. The noise started to disappear around 9 volts... Don'T know why - and was totally gone at 11V... FYI

I TRULY hope this helps someone in the future so that they don't have the same problems.

 

[WannaBoogie]

I think I found the schematics that were referred to in that link. You can see the 50V blue (BLU) tap on the transformer in the Power Supply drawing, and again referenced at the 220 ohm (220R) resistor at the beginning of the switching matrix. Remember, these are not for your specific amp, your tech will need to deciede what value resistor to use for the correct voltage drop from 50V to the 10V you had from your OEM transformer. I hope this helps.Dom

Wow! Thanks Dom... I'm going to send these to him right away. Maybe we can avoid the whole 2nd tranny solution.

Cheers!

 

[94Tremoverb]

This is what I would do:

Run the amp at 100V until the correct transformer is available - it won't do it any harm, although it's probably best to avoid using the Spongy setting for now. (Bold will be roughly equivalent to Spongy at the full voltage.)

Don't mod/hack/bodge it with an extra transformer, some sort of extra circuit or anything else. If Mercury claim that their transformer is an exact replacement then it should be; it's not good enough to supply the wrong one and suggest "ways around" the problem. The correct transformer needs 11 secondary wires, period. 4 on the HT secondary (0V, 50V for the bias, HT1 and HT2), 2 on the LT secondary, 2 on the 5V rectifier filament winding, and 3 on the 6.3VAC filament winding (which is centre tapped, although not shown in that drawing). Without *all* these it cannot work properly. If they claim to have wound the transformer for you specially, why didn't they do it right?

 

[WannaBoogie]

If they claim to have wound the transformer for you specially, why didn't they do it right?

I understand what you are saying...
But, at the time the amp and PT was ordered, (2 months ago now) it was not common knowledge that Mesa had changed the DR to an 11 wire tranny. The way I understand it is that only the TR-Solo had the separate, dedicated leads for the switching matrix until very recently.

Since either way, my warranty is void, I think it is better to make sure that I do the best I can to make sure all power requirements are met... even if it is an inelegant workaround. If Mercury decides to make one in the future, I will probably switch it out again at that time.

The information that Dom has dug up has been invaluable in understanding the problem. And, the tech is also looking into that possibility. But, it all depends on which way he feels will give the best result. The 14V tranny is only about 2" cubed in size. It can nestle nicely behind the other tranny and be unobtrusive. But, the resistor lead from the 50V Bias is the more elegant solution... AS long as it works... I'll be a happy camper.

EDIT: I forgot to mention. I requested a "special order" custom PT to the correct specs, with a 100V primary. I am waiting to hear from them on that. Mercury has already offered to RMA the current tranny. So, if they are willing to custom make one... Then that is definitely the way I will go.

 

[domct203]

The information that Dom has dug up has been invaluable in understanding the problem.

You're welcome bro, I'm glad to be a contributing member of this fine community.

EDIT: I forgot to mention. I requested a "special order" custom PT to the correct specs, with a 100V primary. I am waiting to hear from them on that. Mercury has already offered to RMA the current tranny. So, if they are willing to custom make one... Then that is definitely the way I will go.

IMHO that's what I would do. You could leave the OEM tranny in there for now and run with a step-up tranny, or just wait for the right PT from Mercury. It should only take them 2-3 weeks to make one, plus shipping time.

You bought an amp built to last a lifetime, what's a few weeks extra wait to get it right.

Dom

 

[94Tremoverb]

I understand what you are saying...
But, at the time the amp and PT was ordered, (2 months ago now) it was not common knowledge that Mesa had changed the DR to an 11 wire tranny. The way I understand it is that only the TR-Solo had the separate, dedicated leads for the switching matrix until very recently.

The schematic for the original 3-channel DR from several years back shows the 11 wires. They appear to have used more than one version at some later point - there are pencilled notes on the schematic indicating a different transformer with no 12V winding - but it certainly isn't something new, and Mercury should have checked what the requirement was before sending the transformer out.

Since either way, my warranty is void, I think it is better to make sure that I do the best I can to make sure all power requirements are met... even if it is an inelegant workaround.

No - the best you can do is to use an inelegant workaround that doesn't void the warranty at all, or require any modification to the amp - use a step-up transformer.

The information that Dom has dug up has been invaluable in understanding the problem. And, the tech is also looking into that possibility. But, it all depends on which way he feels will give the best result. The 14V tranny is only about 2" cubed in size. It can nestle nicely behind the other tranny and be unobtrusive. But, the resistor lead from the 50V Bias is the more elegant solution... AS long as it works...

If you *must* do it like this, do it from the 6.3V filament winding, which has a lot more current capacity. In fact, this is the method shown on the older schematic - the 12V winding is shown as NC*.

Fitting an extra transformer is a hack and could cause noise issues. Don't hack your amp to make a temporary half-assed solution when the correct solution is available when Mercury make you the right transformer.

EDIT: I forgot to mention. I requested a "special order" custom PT to the correct specs, with a 100V primary. I am waiting to hear from them on that. Mercury has already offered to RMA the current tranny. So, if they are willing to custom make one...

I thought the whole point was that they already wound one for you specially?

Do it right. Don't do it wrong to 'make do'.


*Edit: good point. Even though that winding is present, does it actually do anything?! On the original 3-ch DR schematic it's shown as 'NC" (not connected). This could mean it goes to two eyelets on the board - just to keep the wires secure - but no further. Get your tech to check this before doing anything else, because if the winding is in fact not used, you can go with the transformer you have and it will work fine.

 

[WannaBoogie]

Ok, I will consider all this before we move forward.

Tremoverb has some strong opinions against the "hack".
Dom thinks I should wait for a new PT,
and I'm just wanting to play. :-D

Tremoverb: Mesa told me that a step-up transformer would void the warranty as well.

I got a message from Paul today at Mercury. He says he will check on the possibility of adding the 12V winding to the DR Tranny with the 100V Primary. But, he seems to indicate that it will take three weeks to get an answer because the owner is on vacation. Dammit!

Tremoverb:Mercury did not CUSTOM make the tranny I purchased. It was just wound-to-order. Meaning it was a catalog item already. And, they began the winding while I was still on the phone with them... Kinda like McDonalds throwing the beef on the grill while you are paying for you Big Mac.

Could you post those old DR schematics or a link to them? I have the Triple Rec Solo that Dom posted. But, I am developing an appreciation for having them around
So, I guess I have been mislead in some respects. I was definitely given the impression that this 11 lead DR was a new thing... and a surprise to Mercury. I only know what I'm told.

Cheers

 

[domct203]

The schematics I posted are for the old 2 channel Dual Recto (note the 2 rectifier tubes in the Power Supply, the Triple has 3). I have the complete set for the 2 channel Dual including preamp and poweramp downloaded on my PC, I'll post them later when I get home.

Dom

 

[WannaBoogie]

The schematics I posted are for the old 2 channel Dual Recto (note the 2 rectifier tubes in the Power Supply, the Triple has 3). I have the complete set for the 2 channel Dual including preamp and poweramp downloaded on my PC, I'll post them later when I get home.

Dom

Yeah, I see that now. With all the reading about triple/dual PTs I get confused.

The Schematics showing the 11 lead PT would be nice too... I think that's what Trem has in-hand.

The more I agonize over it. The more I feel I should listen to you guys and just wait for Mercury to make me a custom tranny to the 11 lead specs... even though it will take forever to get it here.

Cheers, I'm off to work now myself.

 

[94Tremoverb]

Tremoverb: Mesa told me that a step-up transformer would void the warranty as well.

How would they know?! It involves no modification or change to the amp at all, and in the unlikely event that the amp needed warranty work, there is no way of proving that one has been used if you don't tell them. It's ludicrous anyway - by using one, you're doing nothing more than supplying the amp with what it wants.

I got a message from Paul today at Mercury. He says he will check on the possibility of adding the 12V winding to the DR Tranny with the 100V Primary. But, he seems to indicate that it will take three weeks to get an answer because the owner is on vacation. Dammit!

At this point I would certainly check with your tech that the 12V winding actually does anything in your amp. The schematic I have - which is an early 3-ch DR one that I downloaded from the now-dead Schematic Heaven a few years ago - clearly shows 11 wires, but when I checked more closely, the 12V winding is not connected and the LT is derived from the 6.3VAC filament winding. So your amp may work perfectly with the transformer you already have, and this thread was all a dream .

I'm not sure there's any means of attaching files here, but it may still be available somewhere on the web if you search.

If your tech doesn't know how to trace the circuit on the very complex PCB, the simplest way to test is to temporarily disconnect one of the brown wires and see if the amp still works, by the way. If it doesn't, the 12V winding is necessary. Doing this test won't harm anything if it is.

As before, the amp will run perfectly happily at 100V as long as you have Bold selected - that's exactly the same as selecting Spongy with a 120V input, which makes Mesa's ban on altering the supply voltage even more ridiculous.

 

[domct203]

At this point I would certainly check with your tech that the 12V winding actually does anything in your amp.

I think that has already been confirmed:

........
OH! and also, if you under-power this circuit, it will create noticeable noise issues as we discovered by slowly ramping the voltage to the circuit. The noise started to disappear around 9 volts... Don'T know why - and was totally gone at 11V... FYI

Dom

 

[WannaBoogie]

Well, got her back home last night. We aborted the tranny replacement. So, she is still un-violated (for the most part). I will search for a high quality step up transformer to use until....

Still waiting to see if Mercury will agree to manuf the 11 lead PT with a 100V tap. If they do, then it's all good.

I want to REALLY thank you guys for all the information and advice. I have learned a great deal during this episode ;-D

Cheers!