McIntosh 4300V Receiver Problem

[ColonelKurtz]

I'm having a problem with my McIntosh 4300V receiver that started out with the left speaker cutting out at low volume. After turning the volume up, the left speaker would work again. This happened for a couple weeks, until the last couple of days, now both speakers will cut out intermittently at any volume, until I turn the volume up, which seems to work for awhile. I connected my Marantz 2270 to the speakers, and didn't have the problem once, so I'm pretty sure it's the McIntosh receiver. I looked at the schematic online, but can't seem to figure out where the speaker relay(s) is. Can anyone tell me where the speaker relay is located? I've already sprayed all switches and pots with Deoxit D5. Thanks in advance.

 

[62caddy]

The problem may lie in the receiver's internal pre-out/main input connections. The MAC4300 does not use traditional jumpers so the preamp outputs can be used without breaking the line feed to the main amplifier. This is a somewhat common problem with the MAC4280 and MAC4300.

 

[c_dk]

I do not remember if there are 3 or 4 relays.......they really can not be cleaned if they have arced. Replacements are available from most all parts suppliers to be soldered in.

As Eric posted, the make/ break RCA jacks for preout/ amp in and processor loop are also prime candidates for channel issues.

 

[ColonelKurtz]

The problem may lie in the receiver's internal pre-out/main input connections. The MAC4300 does not use traditional jumpers so the preamp outputs can be used without breaking the line feed to the main amplifier. This is a somewhat common problem with the MAC4280 and MAC4300.

Thanks, I'm going to try plugging a clean RCA male plug sprayed with a bit of Deoxit, into and out of the "power amp in" RCA sockets on the back of the receiver several times to see if this will clean the internal contact points.

 

[c_dk]

That is not where they get corroded. The contact is a lever that gets pushed away as you insert the plug. Just use the cable as a jumper to see if it solves your problem.

If that solves it then you can get into the unit and observe how it functions and find your way to assist the Deoxit burnish the contact. If using the jumper does not fix it you will need to look elsewhere.

As per your search for the speaker relays, there are 3 of them, a 4th selects a different transformer secondary winding to increase the current available for the outputs.

The schematic is very detailed and their close proximetry to voltages that can stop your heart if you are not careful causes me to pause.......

 

[ColonelKurtz]

That is not where they get corroded. The contact is a lever that gets pushed away as you insert the plug. Just use the cable as a jumper to see if it solves your problem.

If that solves it then you can get into the unit and observe how it functions and find your way to assist the Deoxit burnish the contact. If using the jumper does not fix it you will need to look elsewhere.

As per your search for the speaker relays, there are 3 of them, a 4th selects a different transformer secondary winding to increase the current available for the outputs.

The schematic is very detailed and their close proximetry to voltages that can stop your heart if you are not careful causes me to pause.......

I was told to try the rca plug cleaning method first... maybe wrong info... I see those relays now. Thanks

 

[c_dk]

The contact that goes bad is on the other side of the RCA post, internal to the jack.......the contact with the plug itself is not compromised. A patch cord as a bypass is your most reliable test.

 

[ColonelKurtz]

The contact that goes bad is on the other side of the RCA post, internal to the jack.......the contact with the plug itself is not compromised. A patch cord as a bypass is your most reliable test.

Yeah I do get what the idea is, and was wondering how the tip of an rca plug would clean the internal contact... Was actually going to go into the receiver and see where that is and if it can be cleaned, but will try the patch first. I've recapped a couple boards before on receivers, so can easily do this...

 

[ColonelKurtz]

Update... not the jumpers... Just tried them, and the left speaker cut out at low volume. All switches have been cleaned. Not sure what else it could be other than transistors/caps. If anyone else can think of anything, please let me know. Thanks.

 

[62caddy]

FWIW - When I had a similar issue with the MAC4300, installing a pair of RCA ICs between the Pre-Out/Main-In jacks did NOT correct the problem of faulty internal connections.

 

[ColonelKurtz]

FWIW - When I had a similar issue with the MAC4300, installing a pair of RCA ICs between the Pre-Out/Main-In jacks did NOT correct the problem of faulty internal connections.

Did you ever find out what the problem was? Thanks

 

[62caddy]

Did you ever find out what the problem was? Thanks

It was still the internal connector relays. I had previously gone through the same thing with an MAC4280 receiver. Throwing in a pair of ICs will not solve the issue with these receivers with internal feed connections - provided of course that's where the problem lies.

 

[ColonelKurtz]

Do tell what the fix was, please... Thanks

 

[62caddy]

I just told you above. The internal connection relays.

*Might not be the exact terminology - but that is what the problem was- both, in a MAC4280 and a MAC4300.

Same symptom - intermittent channel(s) on low volume.

 

[ColonelKurtz]

You didn't say what you did to fix them... Whether cleaned or replaced...

 

[62caddy]

You didn't say what you did to fix them... Whether cleaned or replaced...

Audio Classics replaced them. They said either they cannot be cleaned or that cleaning is only a temp fix. Can't remember the details. Both of the units I sold long ago and sent the repair docs along with them to the next owners so I'm afraid that's all the information I can provide. As I said, installing jumpers/ICs will not correct this issue otherwise I would've simply used the receivers with ICs at the pre-out/main-in jacks.

 

[ColonelKurtz]

Jumpers obviously didn't do it for me either. I just now cleaned them to the best of my ability, and the sound has not dropped out, so far... fingers crossed. Replacement inevitable, then. Thanks.

 

[c_dk]

If you hook up your speakersup to spk2 and the problem only happens when hooked up to spk1 you obviously have a relay issue with the #1 relay. That would be your next at home test before a tech visit.

 

[ColonelKurtz]

Tried all three speaker inputs... 1,2,3 same problem. The problem hasn't happened in the last hour, since I cleaned the internals of the rca's on the power amp-in / pre-outs with Deoxit and a tiny brush made for such cleaning. I also cleaned the rca's of the "LD" section of the receiver, since I have an aux cable to computer plugged in there, and am playing a radio station from Internet radio, at the moment. Hoping this is, at least, a temporary fix. Thanks again for all the help, guys!

 

[ColonelKurtz]

Update: 7 hours later the 4300V is still playing with zero dropouts in sound. Seems like the Deoxit on a small pipe cleaner like brush through the "power amp-in / pre-amp out" sockets worked!