[TV MAN]

So this simple little amp should be a simple little recap, right? Hummm... not this one. This was an eBay find several years ago sold as a "guitar amp". It works, but hadn't used it for some time. I decided to get it running since all it should need are caps and it will work fine ... yeah! As you can see in the pics, the recap has been completed. I'm sure those 2 sand resistors need to be replaced also, 120 ohm, then there's 2 coils off those resistors, not on the schematic. Those go off to the plug on the side of the chassis. Maybe to the phono motor or something. BTW, I DO have a nice 557 I want to restore. I'd thought of just swapping amps and calling it good, but not gonna happen. So what is wrong with this little amp? Well, a little bit of everything! I never get the same sound twice and it just doesn't sound right. I've checked voltages and signal traced without much success. I finally did spot a place on one of the output tube sockets that I saw arcing - to the beat of the music! I cleaned the sockets and ... it got worse. It even started smoking to the beat of the music when I really pushed it. Oh, now I've lost part of my B+ voltages - actually, it just dropped off, and really can't find a reason. So, I'm going to have to pull things apart and replace those 2 output tube sockets and check connections. Oh, I did find a cold solder connection on the cathode of the output tubes, fixed it and still wont behave.

Here's an interesting note ... back when I was a youth in the '70's, I had a VM 557 given to me - actually, I kinda took it. Was my mom's from her high school days in the '50s. Stand and all. I played that thing and played that thing. Loved it. But, like all things, it started to give trouble. It ALWAYS has a hum/hiss in the sound and would sometimes just up and shout out a nice feedback whistle. Mom said it would do that - since new! But, I still loved that old phono! It finally gave it up, volume dropped off, then would suddenly and without warning start blasting. Oh, and for a suitcase record player - that baby would crank! It finally did get so bad that it wasn't really usable so it got taken apart and that was the end. I still remember watching the trash guy throw it in the back of the truck. END.

So, what's so weird is that this amp I'm working on now - exhibits almost the EXACT same problems as that amp I had as a kid! So, I really want to solve this and take notes of just why and what the problems are! Wow! I may even take the original amp out of my present 557 and see how it acts. So, there's a reason I have a 557. It's something from my youth. Something I enjoyed a lot. And missed. So there ya have it. I'll include a schematic, but I'm betting I'm gonna have to completely redo, resistors and all. 

   
   
   

[David]

Time for a stupid question what happens if you flip the plug when plugging in the wall socket? 2nd stupid question have you tried a isolation transformer? I think the NEI changed in 1973 to require 3 prong plugs was something like 1978 before all states said ok. David

[morzh]

For intermittent things...I have a rule: if you have all good tubes, full recap and socket cleaned, it should just work.
Oh...the miniatures, if old, might need some pins cleaning.
Of course, cold solder joints and cracked resistors - could be revealed by light tapping with some plastick stick.

[radiorich]

Hello Tim,
I have a little RCA 45Y-2 that after replacing the capacitors and some other parts it worked but it also started acting up it also uses one of those Sand resistors too plus it has domino mica cap, So I am going to replace both also check for noisy resistors.

Sincerely Richard

[Arran]

Tim;
I was just going to mention the sand resistors, but Richard beat me to it. Those are a replace on sight item with me, they are the only wire wound resistors I have had fail just from sitting on a shelf. They have a habit of corroding, and the connection between the resistive wire and the ends tends to break down, in my opinion they are worth messing with. The two 2 Watt carbon com resistors with the rough bodies should also be checked, they don't behave like sand resistors but they do go up in value.
Regards
Arran