Mark Levinson ML9 problem

[vincentfrowijn]

Hi, does anybody have schematics for this amp?
One of the outputs of my ML-9 is down.
Luckily the whole amplifier has a current protection circuit in the main power supply. When I disconnect the +50 and -50 Volt for the faulty channel from the power supply the other channel works perfect.
I found out that some of the TO3 cased transistors are used for power supply regulation per channel, I suspect that the error is in that part. Having the circuit schematics would make it much easier.
Does anyone have any experience in repairing a Mark Levinson power amp? This model is supposed to be the smaller brother of the ML-3 and the predecessor of the ML-27 power amp, giving 100Wpch/8Ohm, (conservative statement, it delivers even 380W in 2 Ohm!).
The sound is still (or rather was) great and that for an amp built in 1978.

looking forward for any help,
regards,

Vincent

[johanne]

Hello Vincent!

perhaps I can help you, as I know there is no regulated supply in the
ML-9. The two differential gain stages and the output emitter follower
have the same supply rails coupled via resitor/cap filter.

I have the schematic in pdf, the only thing missing is the main power
supply.

This is my first post here and they don't allow me to send a mail.
Please give me your email-adress and I will send you the schematics.
I hope helping you

regards from Harsewinkel
Ralf Johannesmann

[vincentfrowijn]

Hi Ralf,

Thanks for the reply.
Actually through this forum I already received help by email. The items sent were strict confidential.
But the problem looks to be more severe than I thought.
I would be grateful for any help after july 24th, so I'll probably contact you by then.
This is my first thread here too, so I don't know if I'm allowed to send email either. I will try.
thanks again for your offer
regards,

Vincent

[barnabamax]

Hi Johanne,

my name is Massimo and I'm going to buy an old ML9, unfortunately not original at 100%...

However, due to its very cheap price, I'm for buying, for this reason I would like to receive a copy of service manual, so I have the opportunity to bring ML9 to its original configuration.

Thanks in advance, best regards from Italy
Massimo

[perelman]

Hi Johanne,

I have just bought a ML-9 in the US (eBay) for a very fair price and therefore, I would need to change the voltage main supply from 110 to 220 V, as I live in France. I know the transformer that's inside is ready for different voltage supplies, and i suppose that it has to do with a wire connection moving.

I suppose it's not that difficult (am I wrong?), but I would be more at ease if I could rely on the amp electrical schema. I've read higher in the thread that you own such a description and I would be very thankful if you could send it to me, if you don't mind.

Because it's not easy to send PM directly when you're not a very active member (that's my case), I let here my email : jeromeperelman "the usual sign everybody knows" gmail.com.

As you are an electrical engineer, I will gladly pick up any good advice of yours in doing that transformation...

Thank you if you read that post and even more if you can answer me positively.

Kind regards,
Jerome

[tympani1d]

Hello all.
I have an ML-9 that was pulled down for bad hum in rt. channel about 8 years ago.
At that time I replaced a bunch of electrolytic caps stuck it back together to test.
It was just fine.....but I then had the left channel start the same.... so took it back apart, where it has remained. saddly my notes and scribbled diagrams are no longer among the parts!!
I've had literally zero time for audio fun for most of 20 years........but old embers have ignited now.
So the Maggies will have their mylar again resonating!

System: Magneplanar Tympani 1D's -> mid-range; Magneplanar Tympani 3B -> bass; Richard Sequerra custom ribbon tweeters -> high; 4@ Quicksivver 60w mono blocks (8417 + teflon caps) mid-range and tweeters; Levinson ML-9 bass; ARC SP-9 (caps moded) preamp. #4 welding cable speaker cable, 4x44ga Litz wire UDMW Poly Propelyene sleeved interconnects -> bnc connectors; Vendetta Research (aka: John Curl) crossover bass to mid-range; custon passive crossover mid to high.
Now I know you guys here will find all this verifiably "antique" and passe' ...but through these forums those '..tique components will be upgraded. (Quicksilvers already have parts ordered to retube to 6BG6GAs, ML-9 will get the full bypass cap treatment while I'm in there). So we're starting now.
So Thank you for the help and inspiration!

Some day I'll build my long dreamt OTLs for the mid-range and tweeters.

[nagaset]

Originally Posted by johanne

Hello Vincent!

perhaps I can help you, as I know there is no regulated supply in the
ML-9. The two differential gain stages and the output emitter follower
have the same supply rails coupled via resitor/cap filter.

I have the schematic in pdf, the only thing missing is the main power
supply.

This is my first post here and they don't allow me to send a mail.
Please give me your email-adress and I will send you the schematics.
I hope helping you

regards from Harsewinkel
Ralf Johannesmann

Hi Johanne

I'm looking for ML-9 schematics. I have ML-9 which has some noise. I already bring repair shop in NYC. engenneer needs schematics for ML-9.
If you can send me pdf. please send me.

thank you very much

nagaset

[gk7]

Hi Johanne,
I would be interested in getting the schematic per mail too.

[adickson]

Hi johanne we need schematic for ml9, some components are OBS/NLA
like the mps u95 . I hope that register on this you our email
....Adickson

[moxy]

@Vincent .. it's three yrs later.. any luck on the schematic?
irvin