VM 162, the rest of the story.

[William]

It's taken me long enough to write this, I apologize for the delay. It all started with my VM 562 and it not having the correct changer when I purchased it. It was built with a VM 1201 changer. That is the one that has the two slide switches built onto the changer. After a long search, I finally found a 1201 changer and arranged to pick it up. As luck would have it, the party also had a VM 557 and its companion 162 speaker. It was offered, and of course it followed me home. For those that may not know, the VM 562 is a tabletop unit and the VM 557 is the portable version. Portable, let’s just say it has a handle. Changer and amp are the same in both units. Having said that, it's a good thing I bought the 557 as I needed it to figure out how to wire everything up in the 562. All the leads were cut when the wrong changer was added, and the documentation did not offer any info on how it all wired up.

Now, back to the VM 162 speaker/amp. The first thing I did was to bring it up on the Variac. Surprisingly, it fired right up and no HUM. Just because, I plugged my KLH tuner into the input to see what would happen. What I got was surprising. Lots of distortion, and garble sounding. Next, I tried my RCA 45 player. That was some better as the distortion and garble were better, but very low volume. Time to open it up and start the rebuild. I pulled the amp and started by testing the tubes. All good! Next, I flipped it over and started to compare the schematic to what was in the chassis as things did not look quite right. Yup, things were not right. Someone, at some point in time had added extra things. I should have known, as instead of having the normal RCA jack on the back it had a microphone style jack. My guess, it was either used for a PA or a guitar amp. The party that I purchased the 557 and 162 mentioned they had 557 first and found the 162 years later. I’m also guessing they never tried the two of them together as it would not have worked. Or they knew all along that it did not work and decided to sell it to me. Not knowing anything about what the added components did, but guessing they altered the input voltages, I removed them and put things back as shown in the schematic. Again, I fired it up on the Variac and this time things were much improved. No distortion or garble and plenty of volume. I still did not sound quite right, just not as clean as it should be.

My first step in the rebuild was to install the fuse holder. Next, I replaced the electrolytic and paper/wax caps, and did voltage checks just to see where I was at. That was followed by testing all resistors, and only a couple were off. VM seems to use closer tolerance resistors than other electronics I have worked on so that might make a difference. Voltage testing confirmed that things were as they should be per schematic

My next step was a complete cleaning of the cabinet and a little touchup of some flea bites. Next, I put the speakers back in the cabinet, slid the amp back in place, and fired it up. So far so good, so I plug in the RCA 45 player and put on a stack of records. I played both sides of the stack, felt the PT and it was just warm to the touch. Things are looking up and as I set writing this the VM 162 is being used as the companion speaker to the VM 562. Both sounding good.

One more thing to mention that I found to be weird. The 162 has an 8” woofer and a tweeter. The tweeter does not have a crossover cap, and there is not one mentioned in the schematic either. You would think, too much in the volume department would blow the tweeter. Not the case, wide open it just keeps tweeting away. The 162 is a PT powered singled ended amp which is not exactly a match to the 557 or the 562. Both are PT powered and PP and have five tubes total. The 162 only has three tubes. The 557 is up next and the amp is on the bench. I will report on that as I dig into it. Photos to follow, I hope!

[electra225]

Please continue to share this project with us. You do good work, Bill.