tube amp help!!!

[tonyhatchetman]

hi every one i have a ramn 500 i just got looks great but it has not been used in a long time the problem is that i plugged it in and all the tubes light up and every thing but there was a hum noise coming from the transformer so i tryed to go ahead and use it but i started to tune the amp and it went from 100 to 300 watts and then all the big capacitors inside started blowing smoke and oil out like crazy so i unplugged it and let thing clear out and then i plug it back in and i heard popping and crackling from it any ideas what happened.

[Pro-Tech]

You need to get in touch with John Boy at Expert Ele. in Memphis TN. He is the God of the tubes. If he can't fix it or reproduce it, then it don't exist. This gut use to work at MACO back in the glory tube base days.

[tonyhatchetman]

do you know how to get in touch with him?

[Pro-Tech]

I'm not at the store right now, just call information and tell them you need the number to Expert Electronics on Brooks road in Memphis, Tn.

He opens his store around 9 a.m. -Monday thru Friday.

John Boy is also famous for the Tennessee Walking Horse. He is very respected in our industry because of his life time work and design in DX history. Come to think of it he is living breathing American history in the flesh. I hope some day they write a book about him or a movie to let the whole world know that we can enjoy our hobby because of his hard work in perfecting RF power. Him and a hand full of others use to produce great product back in the 70's like MACO, Palamar, Black Cat, to mention a few.

So whatever he tells you to do with your box take it as the gospel truth.

[King Mudduck]

From what you have posted about the amp you can just about plan on have the amp rebuilt from top to bottom. Letting any kind of tube equipment sit for a long time really ruins them and then when you stick power to it after sitting the caps start blowing left and right. It also sounds like the transformer is going bad, now if its just a quite hum then dont sweat it but if it's loud then it needs to go.

[DX_MONKEY]

It was the capacitors. Paper film caps dry up and go bad over time. Should be easy to find and and not too much trouble to replace. Hopefully this will be the only problem and you've got yourself a good amp.


good luck

[chubbypigfarmer]

Old/bad Electrolitic Capacitors took out the rectafier diodes most likely, its pretty common in old tube radios and amps especially when they haven't been run in a long time but its certainly not the end of the world, probably less than $20 in parts.

[209 first class]

i think you deadkeyed too long during tuning. you cant go more than 5 seconds before letting it rest/cool off before resuming tuning on a tube amp. for all you know the capacitors may have held up if tuned. did u speak into the mic before it was tuned ? that would wreck it too. tubes amps are VERY touchy. im a compulsive channel flipper, so im a solid state kinda guy. sorry it happened to you. 2zero9. as a sidenote, i bet u could get another one off ebay for cheaper than it wold cost to get that one fixed. i have bought 7 of them from ebay, and excluding the one that had the tubes come loose inside and broke, they all worked.

[Night Crawler]

Old/bad Electrolitic Capacitors took out the rectafier diodes most likely, its pretty common in old tube radios and amps especially when they haven't been run in a long time but its certainly not the end of the world, probably less than $20 in parts.

That's what happened.

[tonyhatchetman]

well i got all the caps replaced and now when i plug it in the relay keys for a couple of seconds and the transformer is still humming but wail the relay is keyed up there is sparks and popping under the transformer but when it UN keys it quits by the way thanks for the help every one

[King Mudduck]

As i said before. Have it gone through from top to bottom or you will just be **Censored** your money away because you will be replaceing parts left and right until you get **Censored** and chuck it in the trash. Spend the money once, do it right and it will last for many years!

[kb8ym]

the caps are old. most of the time replacing them is all thats necessary.
they dry out with time. dont fire up till u replace.

[Foxhunter]

Like others have said, it was most-likely the old paper/wax capacitors. Those old types will almost all "go up to capacitor heaven" at some point. Below is possibly why the caps blew immediately.

Here is some advice given to me a while back when inquiring with a couple of well-know antique radio restoration & repair men---experts in their field. I know this is common knowledge for many---but for others it's good, solid sound advice---for anyone thinking about powering up an old radio or amplifier unit or other vintage electronic device, that initially wanted to just "plug it in and turn it on".

Whenever anyone takes an old radio or amplifier that hasn't been used for some time---or how long since it's been on is unknown---there are two basic ways to power it up relatively safely. The first way being the best and safest. This should always be done in an area that is safely cleared of surrounding objects for "fire prevention" reasons. Especially since both methods involve leaving the unit on and unattended for lengths of time.

One---the use of a variac. Make sure before doing this that ALL function knobs are set to their lowest settings. Connect the unit in-question to the variac and set the voltage on low. Turn them both on. Gradually you will have to incrementally increase the voltage over a period of time. The old radio restoration guys I've talked with say to do this over a period of DAYS, slowly bringing up the voltage to normal operating household current & voltage. Like in all things, be methodical and show patience---you can't hurry or rush this procedure.

Two---this is done without a variac and a bit more "chancy". Make sure before doing this that ALL function knobs are set to their lowest settings. Plug the unit in to the outlet. Check for anything unusual, noise odors etc. After a small period of time, then turn the unit on. And leave it, for up to a couple of days. Don't do anything to it or with it, especially trying to put the unit under any type of demand or load. Just leave it be and keep an eye on it.

The whole idea behind doing all this is to allow the chance for the capacitors to "reform"---and sometimes they will. The very nature of a capacitor works that way, they degrade over time. But, if still "viable", they will reform and work again. That initial "inrush" surge of current & voltage can blow several things on a unit that hasn't been in operation for a long time.

In the end it's best to replace the old capacitors, but these are the first steps to take if you want to see if the unit is working or worth sinking any time or money into. There are also test units called "capacitor testers" (I have several) that can test & check the capacitor as being viable, dead, or "leaky".

Watch it---there have been instances where the power cord itself was incorrectly wired to the chassis in such a way as to electrocute the man turning it on. The seller may have listed the unit as "not DOA" when you receive it---but YOU may be after plugging it in. A quick but careful interior inspection of the power lead inside the unit's cabinet may be wise and prudent. And taking into consideration the usual warnings of watching for electrocution (even if unplugged) from the interior components.

Just a few things for others to consider who may be visiting the Forum or reading the thread out of curiousity. Hope it helps someone.