VM 562 question

[William]

I need to ask for ideas for a problem I’m experiencing with one of my VM players. My VM562 table-top unit sounds muddy. I really do not have better way to explain it, it just sounds muddy. Maybe not clear would be another way to say it.

This model has a 5 tube amplifier. EL84/6BQ5 in PP. EZ81 rectifier. 6AU6 and a 12AX7 in the preamp. To me the schematic looks like it might be Ultra Linear. It looks like there is a center tap from the output transformer. There are two speakers, both 8,” but they do not have the same paper cones. The changer is a 1200 series with two switches. One switches off the motor so the amp can be used for a aux. something. The other switch, switches between stereo and mono. There is a direct RCA output jack on the back that comes directly from the stereo cartridge. The cartridge is a EV26. There is a matching, which I do not have, speaker/amp that can go with it to make it stereo. In the mono mode is where it sounds muddy, or not clear. In stereo it is better, but still not perfect.

To add insult to injury, I have a VM 557 portable record player. The 562 and 557 amps are the same. The changer is the same. The only difference is the 557 has a 5X7 speaker in place of one of the 8” speakers. There is not room for two 8” speakers. The 8” speaker that is in the 557 is exactly like one of the 8” speakers in the 562. The VM557 was also offered with a matching, sort of, speaker/amp. I do have that speaker. The amp is smaller and less powerful in the aux., amp/speaker and it contains a 6” and a 4” speaker. The VM 557 in mono mode sounds much better than the VM 562 in mono mode. The 557 has a new replacement cartridge.

Does anyone have any suggestions on what the problem might be? I’m going to try swapping out tubes between the units, and I might try swapping changers just to see of the cartridge is the problem. Any other thoughts would be appreciated. I have provided a link to Gary's site so you can see what a VM562 looks like, and I have also included the schematic for the amp.

https://www.thevoiceofmusic.com/popup_p ... &TITLE=562

Thank you,
Bill

[electra225]

Is the distortion there when it is first turned on? Or does it take awhile for it to appear? Have you checked voltages at the rectifier cathode? At the plates of the output tubes? Have you checked cathode voltages on the output tubes? Grid voltages? Does grid voltage climb as the tubes get hotter? Subbing the speaker and tubes won't hurt, either. You are on the right track, just gotta run the culprit to ground. A 6X4 is an interesting rectifier to power 6BQ5's. More typical to see a 6CA4 or 5Y3. You had this one done and it worked well, right? I reckon a cartridge could go wonky after it's fixed, but that is pushing it, I'd think. Good luck.

[hermitcrab]

By muddy do you mean not clear or bright?... agree with Greg, check everything in the audio output up to and including the speakers.... also try it with only one output tube in circuit on each side... maybe one side of the output transformer winding is a problem?.... do you have anther source to input into the amp to see if there is a difference in the sound confirming the cart is ok ?

[William]

I have neglected to continue with this thread. Mostly because I have been lazy, and I had knee surgery. It's on my list of things to do, but maybe not at the top right now. I still need to get the RCA changer off the bench as well as the big Motorola table radio. Stay tuned, it will happen eventually.

Bill

[TC Chris]

How about checking the speakers for a rubbing voice coil? You could hook up each speaker to a known good source and see if either gives you a vaguely unhappy output. Your schematic shows a "tuner" input switch on the turntable. Running a tuner or just about any other high-level source into that would tell you if it's the cartridge or something downstream from there.

Chris Campbell

[William]

Thanks, Chris. I have checked out the speakers and they are good but that is as far as I got before other things interrupted me. I'm almost caught up with spring chores, so I hope to get back at it soon.

Bill

[William]

So, 2 plus years later I finally have the VM562 sorted, and it sounds great. There were several things that were causing the problem.

First, all measurements in the amp were good, tubes were good, speakers were good, and I even installed a new cartridge just to be sure, but it still did not sound right.

I tried cleaning the controls again including the two slide switches. After cleaning the controls, I discovered I had totally lost the mono side of the switch and on the stereo side the RH channel sounded weak and kind of distorted. While a record was playing I wiggled the switch which made the stereo side kind of cut in and out and the RH channel would sound better but then go back to sounding bad. Mono, was still dead. I tried cleaning the switch one more time with no results.

At this point I reached out to Gary to inquire if the switch was still available. Good news, it was so I ordered one up along with a few other things that I needed. Once the switch arrived, I installed it only to find I still had no mono, but the stereo side was working. Now I am thinking I have something wired wrong as these double switch models are unique and it does not take much to get wires turned around even if you documented where everything went. Neither VM nor Sam's shows how these switches are wired. Since my VM557 has the same amp, and everything is wired the same I checked that to make sure I had everything correct. Nope, I had two wires turned around. Good, I finally have the problem solved, but with my luck, that was not the case.

Ok, what am I missing. I do not have a bad cartridge because I have stereo. Maybe the new switch is bad, after all it is NOS so like the original one it is 60 plus years old. Before I looked like an idiot, I went back to the drawing board starting at the source (the cartridge) and working my way to the amp. I took my trusty VTVM set on ohms and started poking around.

The first thing I tested was the new switch and it tested good. Next, I tested the tuner/phono switch. Besides turning off the phono motor it also has audio properties built into it. That switch also tests good. Hmm. If the cartridge is good, the mono/stereo switch is good and the tuner/phono switch is good, that only means one thing, the problem must be in the wires coming from the cartridge and going to the switches. But if that were the case, why do I get stereo??? Just to make sure, I ran continuity on each of the three wires. RH wire, good, LH wire good, ground/common wire dead. WHAT! How can I have stereo continues to go through my mind. To finish my story, as you are all probably bored by now, the ground/common wire was the culprit, and the break was half way down the tone arm. How in the world the break happened there is beyond me, that is all protected by the tone arm.

Needless to say, I am a happy camper now and the VM562 sounds great in both mono and stereo.

From Gary's site, this is what a VM562 looks like. Mine does not have the legs.

https://www.thevoiceofmusic.com/popup_p ... &TITLE=562

Bill

[TC Chris]

We love success stories....

Chris Campbell

[William]

Thanks, Chris, it took long enough.

Bill

[electra225]

Yeah, Bill, but you are Mr. VM. Success was inevitable.....

Good job!! The problem child projects sound the best when you get them sorted...

[William]

Thank you.

Bill