'51 Deluxe 5B3?

[Mike62Jazz]

What does the "Dry" refer to on Astron Minimite Dry Electrolytic Caps? Also is the cardboard cylinder supposed to be able to spin while the ends remain stationary?
Sorry if this is a Newbie question.

[52 Bill]

What does the "Dry" refer to on Astron Minimite Dry Electrolytic Caps? Also is the cardboard cylinder supposed to be able to spin while the ends remain stationary?
Sorry if this is a Newbie question.

Welcome to the board.

Dry refers to the way the cap manufactured with a "dry" electrolytic paste.

The cardboard sleeve is there to insulate the metal case from the outside world. Modern caps use a heat-shrink sleeve to do this. So yes it will spin around on the case.

[Mike62Jazz]

52 Bill,
Thanks for the info! I have been talking about this amp on another forum and it was suggested I come here. This is a friends amp that used to be his Dads. I took it apart to document and identify year by Serial, Pot codes, speaker code, etc. I was cautioned not to turn it on as it may harm the amp unless it gets a cap job. I am not a tech, but do have some basic skills, the tools, schematic, and some modding experience. The owner would like me to do the work but I told him I would have to do some research. I will only do this IF I feel comfortable. I will link some pics of the amp and would appreciate any tips, suggestions, cautions etc. Also, would you, or anyone reading this, suggest replacing all the Caps and with what type and Brand?

Thanks, Mike

http://zip.smugmug.com/gallery/67410...30538660_proeJ

[52 Bill]

...I was cautioned not to turn it on as it may harm the amp unless it gets a cap job.

I don't think that you'll do any real damage by turning it on. When was the last time it was turned on? Some people will recommend that you replace all of the caps or at least all of the electrolytics. I prefer to take things one step at a time. See what the amp needs and then proceed.

Try plugging it in with either a variac or a light bulb limiter. If you don't have a light bulb limiter or a variac, pull all of the tubes, plug it in and turn it on. You should see the pilot lamp go on. Check the output of the power transformer for ac voltages per the schematic. As long as they are close then proceed by installing the rectifier tube.

If you get reasonable dc voltages, check the B+ line for ac ripple. If it's under a few volts, then plug in the other tubes and power it up. If it needs filter caps you'll hear an audible hum. As long as the hum is not too loud, you can still check the functions of the other circuits.

[Marc]

Mike,
A '51 is a sure bet for at least filter caps and proabably all of the electrolytics. I like using a light bulb limiter for amps like this, it's like a soft start. The coupling caps may also be leaky. My '57 Harvard filter caps were Ok but the astron coupling caps were leaky as a sieve.I changed them to Mallory 150's and the amp came alive.

What ever you do save the parts in a baggie for the owner. If he ever gets a hankering to sell it, some collectors will pay more for the orignal parts with the amp even though they aren't fit for more than the landfill.

Marc

[Mike62Jazz]

Marc,
Did you look at the pics in the link? The coupling caps were replaced years ago. They are the Orange drops in the middle.
Thanks for your input.
Bill 52, the owner said he fired it up about a year ago. He said it sounded fine.
Mike

[Mike62Jazz]

I don't think that you'll do any real damage by turning it on. When was the last time it was turned on? Some people will recommend that you replace all of the caps or at least all of the electrolytics. I prefer to take things one step at a time. See what the amp needs and then proceed.

Try plugging it in with either a variac or a light bulb limiter. If you don't have a light bulb limiter or a variac, pull all of the tubes, plug it in and turn it on. You should see the pilot lamp go on. Check the output of the power transformer for ac voltages per the schematic. As long as they are close then proceed by installing the rectifier tube.

If you get reasonable dc voltages, check the B+ line for ac ripple. If it's under a few volts, then plug in the other tubes and power it up. If it needs filter caps you'll hear an audible hum. As long as the hum is not too loud, you can still check the functions of the other circuits.

52 Bill, Could you take me through the procedure for doing the above, safely?

Thanks, Mike

[52 Bill]

52 Bill, Could you take me through the procedure for doing the above, safely?

Thanks, Mike

I thought I already did.

If the amp has been worked on/turned on recently, plug it in and turn it on. Listen to the amp, watch for signs of overheating or other abnormalities.

From your original post, I thought that you meant that this amp had been sitting for years without having been turned on.

[Mike62Jazz]

52 Bill,

The owner says he turned it on within the last year or so. I don't know if that constitutes recently or not. I know it isn't used on a regular basis. As far as it being worked on, the work was done 10-15 years ago. I'm still learning about how tube amps work. As far as the schematic, I don't see the AC voltages on the schematic, I'm trying to figure that out. Where , and how, do I check for reasonable DC Voltages, where do I check the B+ line for AC ripple. If this sounds like I don't know what I'm doing, you're probably right <VBG>. If you suggest I "Walk away from the Amp", I will. My intent is to learn as much as I can. I am reading as much as I can find about this amp and it is interesting. I appreciate your time and hope I am conveying my thoughts clearly.

[Mike62Jazz]

Well, I decided to fire it up and see what happens. The night before I turned it on, I used Deoxit to clean the pots, jacks, tube pins and sockets. I turned it on and it was quiet for a minute or two. Plugged in a guitar and strummed a few chords. After 3 or 4 minutes it started to crackle and pop mildly. some static type noises trailing notes. I promptly turned it off. From what I read, it may be just a bad tube but I'm going to take the advice of a tech I talked to who said, "Do you really want to try to learn about tube amps by practicing on someone else's Vintage Fender"? I am going to give the amp back to the owner with the recomendations I received here, and elsewhere, along with the Techs' Phone number.

Thanks Again, Mike