A little problem with my MA6200 amp - help requested

[kevzep]

Regarding conversion in MC INTOSH products :
none MC INTOSH is using 240V DC V Relays
there is only 110V DC V Relays and depending how your MA6200 conversion has been done but I am sure that 240V is not right ! 240V voltage conversion made here over 42 years without any trouble
Regarding MA6200 : there is 087030 K2 110VDCV for mains soldered on PCB , with C703 10µF/160V (who will explode if connected to 240V ! )
and K1 087019 DC24V insert to a socket
I honestly don't understand how this "tech" can make a mistake ! physicaly impossible to use one relay instead the other !
other question ?

Yes that is indeed correct isn't it Patrice, as I know all too well!! You need the correct 120-230V conversion information otherwise you burn up the auto on relay...

Definitely we need some more information as to what is in this unit to give the right guidance here, I would think if there is a 240V relay in there anywhere, then other parts of the circuit could be stressed out by over voltage.

 

[kevzep]

The problem with the Perraux products here in the states as I remember,was that the regulation circuits burned up trying to overcome the mains supply voltage sag. The DC supply voltages would drop below the input threshold of the regulator circuits and they would fail. As a non Perraux dealer I did not have first hand info on this other than disgrunted customer complaints and a interesting conversation with the former importer over a few brews late in the day at a CES. This was at his new startup Modial?? If I remember correctly a Tony??? Too many years ago...!!

Getting a bit off topic. But for the fun of it anyway, no soft start, no protection circuit, no speaker relay.....
Very agricultural amplifiers, not my scene!!
They used to burn up power switches from the inrush current on start up.....I'm having flashbacks to some frustrating times under the hood of many a PMF amplifier....Yuck!!

 

[kevzep]

I think the way forward here is to replace both relays, and make sure no damage has been done to the Auto On circuit.
If you have 230V on that for too long, things definitely fry up...

 

[FauxHall]

I also see a 160v cap on the schematic that now sees 240VAC. This is on K2 - C703

I wondered if that was changed in my unit. I'll check this weekend. However, there is no indication that K2 has problems as the general power supply is functioning.

K1 looks like it sees 24VDC across the coil (46 - 22 = 24)

The Omron spec sheet says pickup voltage is 80% max and dropout voltage is 10% min.

With the wrong coil, maybe it can't move the contacts as it sees inadequate voltage? So this might be a better choice...

 

[clinic-audio]

Your choice is not good
here is what a MA6200 speaker relay look like :

 

[FauxHall]

Your choice is not good
here is what a MA6200 speaker relay look like :

View attachment 962295

That's exactly what mine looks like and it matches the Omron spec sheet. This gives me confidence! Thanks. Mouser may have the wrong image

 

[clinic-audio]

Hello

here are some pictures of an original MA6200 speaker relay :









we can not be more precise

 

[clinic-audio]

I am sorry , but again people trying to do things themselves don't know about what they are talking about

Since the beginning you make confusion between power relay (110V DC )and speaker relay (24V DC ) !

see your own picture and you will see that confusion I am talking about

 

[FauxHall]

Got it now. The last relay spec is correct, I just had the wrong physical location.

Hope you guys aren't this rough on all your apprenticesl The only reason I'm doing this myself is the lack of competent techs in this corner of the planet.

 

[Hipocrates]

but again people trying to do things themselves don't know about what they are talking about

First... thanks for sharing the info.
Second:
Come on man, can you be happy just to help? Why do you have to nag and complain about it?
If he, or me or anyone is looking for help in this forum is for a reason, can't u see it? Why this attitude?
All this fuss and passive aggressive crap... just for a little information about some cheap relays for an old piece of gear that you and a couple fellows, probably knows more than anyone here.
I don't get it.

 

[FauxHall]

Reminds me of a movie - "Grumpy Old Men" - me included!

Just won a matching MR77. They will make a pretty pair in my apartment.

Should I replace the PSU main caps and add bypass caps in the amp? Might as well make one big Mouser order.

 

[kevzep]

Firstly, what needs to be established, is whether the 120V to 240V conversion has been done properly. If it has not been done properly, you will burn up relays and the Auto On circuit will be running way way over voltage.
So that needs to be put right.
I suspect it is wrong if there is 240VAC on some parts of the Auto on circuit.

The line bypass capacitors need to be changed, I use 1000V X/Y caps, the ones that go open when they fail instead of shorting out.
There are most likely a few other components that should have been changed too.

If there is a 240V relay in the Auto On position, it is wrong, and as earlier stated other parts of the circuit will be running over voltage, including those Line Bypass caps.

Now, getting the service bulletin is not that easy.
So, you need a very good tech to look at the design there and figure out what needs to happen.

I know this because I had a bad conversion done to my C32, it ran for nearly 12months with the Auto On circuit running 100% overvoltage, then it burned up, took out the relay and a resistor, and also blew out one of the electrolytic caps, so you might have more issues than just the speaker relay failing, which by the way had nothing to do with the voltage conversion.

I think this is where we are all getting confused.

Remember Patrice (clinic-audio) is in France, he speaks little English and sometimes comes across a little forward at times....But has the knowledge and can help.

 

[FauxHall]

The are two voltage ratings for a relay. One is for the contacts and the higher the better in general.

The second is for the coil and this needs to match the application closely.

 

[kevzep]

The are two voltage ratings for a relay. One is for the contacts and the higher the better in general.

The second is for the coil and this needs to match the application closely.

Yes you are correct, I am talking about the solenoid voltage though which is critical for correct placement in the circuit, I neglected to specify that.
I look at the current rating of the actual switching contacts. Thats the easy part though....

Are you confident enough to have a look through this, to make sure the conversion has been done correctly?

FYI, The big issue with the Auto On circuit is that it is on the primary side of the power transformer, and what McIntosh do for the 120-240 conversion is they put a center tap on the primary winding which then runs the Auto On circuit at 120V which is its designed to, common mistake is to just change the two primary windings from parallel to series to run 240V, which then if you do not know how it works, puts 240V on the Auto On circuit
This is not in the service manual, and not commonly known, if you have a very clever tech they might be able to work it out, or we can guide you through, but we would have to know the colour code of the primary windings....this is where we need to help of the ex-Mc service guys...

 

[clinic-audio]

Come on man, can you be happy just to help ? I am sorry but I did and was maybe the first to tell where the problem was !

Why do you have to nag and complain about it ? I am not nag but just complain yes , complain that we loose time (3 pages ) and nothing is done .

You are right I know many things (42 years working on Mcintosh product that's a lot ) but if one owner is not able to understand what is written on the relay cover (see my picture and you will see 240V and it is the speaker relay !! ) coil is 24V DC
that's what I mean when I say "dont know what they are talking about " and they bring confusion
I have nothing against Fauxhall and if he get trouble with his unit send me a PM . I have many customers worldwide ! not only in France

 

[Hipocrates]

complain that we loose time (3 pages ) and nothing is done .

Fair enough.

 

[FauxHall]

I think I've got the correct part number to correct the butchering jumper so I can that as critical progress!

Thanks gang!

 

[twiiii]

One of my jobs over the years was repairing Telephone switch boards that used stepping switches and all sorts of individual relays per communication link. The better boards used bifurcated contacts. i.e. to two pairs doing the work of one simultaneously. Some used gold others used silver as silver oxide will conduct as well as the silver itself. Gold isn't supposed to oxidize, but seems to collect pollution more than the silver contacts. Depending on the contact surface design different cleaning procedures are to be used. A burnishing tool will get the problem solved but will guarantee future failure much sooner. So if you can't clean the the contacts with chemicals using lint free paper. Replace the relay. $100.00 dollar bills work when you are trying to impress some greenhorn, but a $1.00 bill works just as well. I used Miller Stephens Con-tact Renu when cleaning switch boards. Works great on rotary switches, and on crossbar switch systems, too. I had issues with C-28, C-29, 2120, 2125, 2205 and 2200 amp relays consistently over the years out in the field. Especially in clubs with polluted environments.

Revox used 4PDT relays in their recorders and they were always failing. I would remove the supplied relays and install hermetically sealer Potter-Blumfield relays. No more issues. My Revoxs and friends Revoxs automatically got sealed relays when purchased. If folks were cheap they got new relays for free when brought in the shop from Revox.

 

[FauxHall]

Parts ordered! Besides the speaker protection relay, I got main power supply caps. I upgraded from the 12000 mic originals to 16000. They are the same sixe and the the originals were -10%/+75%. While the new ones are +/- 20% so the new ones won't be oversized. Same dimensions.

I also got the low voltage power supply caps of 2200 mics at 16vdc just in case. I don't solder so I could replace the main caps as they have screw terminals.

I'll look for lower amperage fuses at the local Ace Hardware and replace them if I can find them.

Thanks for all the help and tutelage. Your expertise has been greatly appreciated!

 

[FauxHall]

Surprise! So I ordered from Mouser but I think they ship to the UAE from Munich.

Before they would ship I had to complete and return a "Customer End-User Certificate" declaring that I was not a past violator of US export controls nor on the proscribed list of individuals or businesses. Glad to see that someone is watching.

My guess is that the big power capacitors have dual use in fusing or initiators for nuclear weapons.

Fair enough. Funny that I had to complete these forms when I shipped out nuclear power plant equipment to Taiwan when I worked for General Electric Nuclear in San Jose.