diytube.com

This little beauty landed on my bench this weekend. Something wrong with channel 2, sounds like a small rock crusher with no signal.









Has all these odd flying connections.







Don

Just like with Fender amps, the schematic has some fairly obvious (intentional) flaws, like missing grounds, .around the vibrato circuit.
And "V3" appears to be the two 6V6s.

I dunno about their technique using the chassis as the ground, that's just asking for trouble, groundloops, etc, and of course, the ever-popular "switch on one side of the line, and the fuse on the other side" primary wiring. But then with a two-prong, unpolarized plug, it's always a matter of being a 50/50 probability. ...

Looks like a nice basis for a major Hammertone Upgrade.

/ed B

Three prong plug and solve the rock crusher noise and out it goes. The owner tells me he has been zapped by it a few times. The amp is as quiet as anything I've worked on yet. Like the Belltone I worked on previously, it is simple and effective, but only 10 watts.

When I look at a schematic like this, I don't look too closely detail-wise. More like just trying to get a feel for how it's wired up and which tube does what. So I'd never notice the errors, just general ideas.

Don

Recapped and making a whopping 11.25 watts.







Hey, Ed! Someone in the factory saw fit to correct the schematic between the one I downloaded and the one on the amp I have:





Someone please explain that phase invertor! Wait a minute..I see it now. It's just a badly drawn split load.

Don

Hi Don,
I was poking around today looking for advice in old threads. I picked up a 1949 Ampro Stylist projector the other day and want to use the amplifier chassis to build a small push pull guitar amp. From the date codes on the caps they are original. I read somewhere that I should scrap the electrolytic caps if they are more than 10 years old (I guess 61 years counts!!), but what about the non-electrolytic caps?

I am asking in this thread because from looking at your pictures some of the caps are replaced and some are older (Maybe the originals? Is what I am seeing correct?).

I have an isolation transformer coming in the mail, and I ordered all new caps and resistors for a couple of Champs today. I know the Champ is not push pull, I am figuring that I may get lucky and have the right values once I find a schematic for a low wattage push pull series filament amp. If all else fails I have a PT and OT for a Champ, I just did not want to drill out the rivets for the existing OT.

Thanks, and have a good one,
Dan

It all depends on how much you want to spend. Power supply electrolytics are over $30 per to replace so it is worth it to see if they're any good before replacing them. Any caps with a wax covering should go ASAP. Ceramics never need replacing although some like to swap them out as they are not linear but have a hysteresis like response, supposedly. Golden ears insist they can hear the difference. For guitar amps non linear is good in that it can generate even harmonics. In the harmony, there is and electrolytic bypassing the cathode resistor on the output tubes. At 25 uF and 25 V it is cheap and plentiful to buy, therefore, replace it.

The Champ is a great circuit. I have scratch built two for customers and they Love them. Only 5 watts tho...

Why do you want a series filament amp?

Don

dhuebert wrote:It all depends on how much you want to spend. Power supply electrolytics are over $30 per to replace so it is worth it to see if they're any good before replacing them. Any caps with a wax covering should go ASAP. Ceramics never need replacing although some like to swap them out as they are not linear but have a hysteresis like response, supposedly. Golden ears insist they can hear the difference. For guitar amps non linear is good in that it can generate even harmonics. In the harmony, there is and electrolytic bypassing the cathode resistor on the output tubes. At 25 uF and 25 V it is cheap and plentiful to buy, therefore, replace it.
Don

Darn! The Ampro is full of wax covered caps. I was hoping for some extra wax covered mojo

Regarding wanting a series filament amp: I just wanted to try reusing the hardware I have for this, and to hear how the series filament amps sounded. I am surprised to hear people say that some of them sound so good, I figured they would be humming like crazy with the limited amount of rectification and filtering I have seen in some, but I don't have much experience.

I will probably see what I can put together from the parts bin, and if I don't like it I will use the chassis for a Champ. I have all of the parts for that here also.

Thanks again Don, I enjoy reading your posts.