# Vintage Traynor 4 channel power mixer problem



## Rick31797 (Apr 20, 2007)

I would imagine its not easy too diagnose problems this way, but thought i would explain what this mixer is doing and not doing maybe somebody here with much more knowledge could narrow the issue down..

This mixer will power up, when i plug anything into each channel i get basically nothing.. i hear a very faint sound... but none of the controls work, volume on each channel or master volume..

If i plug anything in the PA IN , the input on the front of the mixer it will work.. but doing this it bypasses the mixer section and runs straight through the amplifier section of the amp.....so this tells me the amplifier is working., but the whole mixer part of the unit is not.. any ideas..


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## nonreverb (Sep 19, 2006)

Is it tube or solid state?



Rick31797 said:


> I would imagine its not easy too diagnose problems this way, but thought i would explain what this mixer is doing and not doing maybe somebody here with much more knowledge could narrow the issue down..
> 
> This mixer will power up, when i plug anything into each channel i get basically nothing.. i hear a very faint sound... but none of the controls work, volume on each channel or master volume..
> 
> If i plug anything in the PA IN , the input on the front of the mixer it will work.. but doing this it bypasses the mixer section and runs straight through the amplifier section of the amp.....so this tells me the amplifier is working., but the whole mixer part of the unit is not.. any ideas..


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## Rick31797 (Apr 20, 2007)

It is solid state..


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## nonreverb (Sep 19, 2006)

Does it have a pre out as well as the PA in?


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## Rick31797 (Apr 20, 2007)

here is what it looks like, there is no pre -out , has main out

Traynor 4200 Mixer Amplifier | eBay


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## nonreverb (Sep 19, 2006)

Ah yes the 'ol tried and true 4200 mixer. Traynor sold a sh*y load of those things in the day. Let me see what I can find...


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## nonreverb (Sep 19, 2006)

OK, I took a peek at the schematic. Just to satisfy my curiousity, place a jumper between the Main-out and pre-in and let me know what happens...
a small patch cable will do.


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## Rick31797 (Apr 20, 2007)

ok will do that tomorrow and let you know..thanks


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## loudtubeamps (Feb 2, 2012)

nonreverb said:


> OK, I took a peek at the schematic. Just to satisfy my curiousity, place a jumper between the Main-out and pre-in and let me know what happens...
> a small patch cable will do.


Correct me if I'm mistaken. Didn't those amps use alot of Molex connectors?
I seem to remember those connectors causing audio path problems over time in numerous electronic gear.
Studiomaster boards come to mind and spending tons of time hardwiring to eliminated the unreliable Molex connections. 
Cheers, doug


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## Rick31797 (Apr 20, 2007)

The Molex connectors is that, those plastic 4 pin connectors you see in computers, or they may be new, back in the 80's they may have been different..


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## loudtubeamps (Feb 2, 2012)

Rick31797 said:


> The Molex connectors is that, those plastic 4 pin connectors you see in computers, or they may be new, back in the 80's they may have been different..


I don't see them as often and a google search of images only gave me the male header.








The female inline connector had "push and grab" clips for each cable. You shoved the wire into the clip with a special tool. The clip pierced the insulaton and grabbed the wire making the connection.


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## Rick31797 (Apr 20, 2007)

I will put some pictures on...

I also tried the jumper from main out to preamp in and nothing happened...


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## Rick31797 (Apr 20, 2007)

*traynor*


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## jb welder (Sep 14, 2010)

Check for your plus and minus 15V rails from the power supply section.


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## Rick31797 (Apr 20, 2007)

> Check for your plus and minus 15V rails from the power supply section.


As i mentioned in the beginning this mixer is not dead... if i plug into the PA IN jack i get power..but thats all..

would this test still apply.

another thing i noticed today... if i plug into any one of the 4 channels i can hear a very faint sound, i was using my drum machine... i only hear this sound if i turn up the reverb switch on the channel i am using.. if i unhook the wires at the reverb tank.. then i get no faint sound at all..


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## dtsaudio (Apr 15, 2009)

jb has something there, except that is 12VDC that you need. There will be +12 and -12V rails, these are derived from the +/-35v rails of the power amp section. There are four 330 ohm resistors that drop the voltage. Check those.


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## jb welder (Sep 14, 2010)

Thanks for the correction Dan. I mentioned the low voltage supplies because (if memory serves) the power amp section does not use them whereas the mixer section does. 
So Rick, you could measure at the regulators, or at the appropriate pins of any of the IC's, for the plus and minus 12Volts.
Otherwise, the muting Fet's were very common faults with these, not sure if they were before or after the PA in jack.
Perhaps nonreverb could be so kind as to post the schematic. I can't find it online anywhere.


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## nonreverb (Sep 19, 2006)

Seek and ye shall find....aint the best but it'll do...
IC2b? looks like a candidate or IC2c? (can't read that small print) Located at the master volume and just before main out. 
As stated earlier, the +12v or -12V rails could be the problem. Best to check those before you go further.

Traynor MX4200 Voice Mixer Circuit Diagram


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## dtsaudio (Apr 15, 2009)

Definitely IC2 could be the problem. It appears to be a quad opamp.
I have the schematic as a pdf if anyone's interested. It might be easier to read than the gif.


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## jb welder (Sep 14, 2010)

OK, thanks for the schematic. It was the MX that threw me off when I was searching (no such thing as a Traynor MX4200). But that is a 4200 schematic. Also, the regulators and mute Fet's I mentioned are not shown so they must only be in the 6400. Sorry for the confusion.

So Rick: The 3403 IC's should have about +12V at pin 4, -12V at pin 11.


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## Rick31797 (Apr 20, 2007)

Thanks everyone great help, i will take a look today...


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## Rick31797 (Apr 20, 2007)

I had to take this mixer in to have a tech take a look at it, the bad news is its just not worth fixing, too much time would be involved, but also you guys were right on the money as too were the problem was... Rick


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## Lafite (May 16, 2009)

I also have one of these old traynor mixer amps. My works fine, except if I plug a mic with an xlr connecter into either of the two channels that have both an xlr and 1/4" input, it doesn't work. But if I put a 1/4" adapter on the same xlr cable and plug it into the 1/4" input in the same channel, it does work. It would seem odd that both xlr inputs would be faulty when everything else works. Maybe I'm doing something wrong, like the xlr inputs need a preamp in front of them or something? Enquiring minds want to know (even if I am missing something stupidly obvious).f


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## Rick31797 (Apr 20, 2007)

It should work regardless which input you use, it would seem odd why both XLR would not work unless they they are linked inside some way, for some reason, i really don't know , i am not a tech, somebody here could explain..


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## shoretyus (Jan 6, 2007)

Rick31797 said:


> It should work regardless which input you use, it would seem odd why both XLR would not work unless they they are linked inside some way, for some reason, i really don't know , i am not a tech, somebody here could explain..


Maybe there is a bad solder joint in the XLR connector.


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## Wild Bill (May 3, 2006)

Lafite said:


> I also have one of these old traynor mixer amps. My works fine, except if I plug a mic with an xlr connecter into either of the two channels that have both an xlr and 1/4" input, it doesn't work. But if I put a 1/4" adapter on the same xlr cable and plug it into the 1/4" input in the same channel, it does work. It would seem odd that both xlr inputs would be faulty when everything else works. Maybe I'm doing something wrong, like the xlr inputs need a preamp in front of them or something? Enquiring minds want to know (even if I am missing something stupidly obvious).f


I couldn't find a schematic on the Net so I am going by memory but back in the old days most of Traynors powered mixers were sold without hi-low impedance transformers.

XLR connectors normally are used with two-wire balanced line mic cords for a low impedance, low level signal. The advantage is that you can then use very long mic cords without high losses and hum pickup. 1/4" plugs and jacks are used for single wire mic cords with high-impedance mics - which are much cheaper but you have to use a cord less than 10 feet tops or you will start to get problems.

So mixers were sold with XLRs installed but no matching transformers so you could actually USE those kinds of microphones! The transformers were sold as accessories. They were a bit expensive - $50 each was not unusual. So they would not be installed in plug in sockets on the chassis as standard items. Also because of the cost, if guys had only one or two low-impedance XLR style mics they would only buy enough transformers for what they had.

I'm betting something similar may be going on with your mixer. If I could peek at a schematic I could tell right away.

Wild Bill/Busen Amps


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## Lafite (May 16, 2009)

Wild Bill said:


> I couldn't find a schematic on the Net so I am going by memory but back in the old days most of Traynors powered mixers were sold without hi-low impedance transformers.
> 
> XLR connectors normally are used with two-wire balanced line mic cords for a low impedance, low level signal. The advantage is that you can then use very long mic cords without high losses and hum pickup. 1/4" plugs and jacks are used for single wire mic cords with high-impedance mics - which are much cheaper but you have to use a cord less than 10 feet tops or you will start to get problems.
> 
> ...


Thanks, this sounds like the problem. I can't see two XLR's failing where the two corresponding 1/4 jacks work fine. Here is the link to the schematic if you would care to take a peek. Thanks again for sharing your knowledge. 

Traynor Diagrams, Schematics and Service Manuals for FREE


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