• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Pops and Hisses from garage sale...

I purchanced a Bell Sound Systems Tube Amp from a garage sale for $30 bucks and all the tubes lit up. I pluged it into a speaker and a cd player and it produces music fine... sounds great!! Although during the silent moments the pops and hisses are very apparent. I bought it so i can learn about tube amps and maybe i'll get a chance to clean one up and fix it. Looks like i got what i was looking for. Does anyone have any suggestions where i should start to trouble shoot, or any books that would help.

Thanks,

Virgil
 
Hi, when you get pops and hisses in a tube amp it can be a number of things. Most likely are bad high voltage connections such as dirty pins on a tube socket or a loose solder joint. Other less likely causes are a gassy tube or a microphonic tube or a dirty potentiometer for adjustment of some sort. You first try should be to try and clean the tube sockets as well as you can but carefully and don't use a cleaner that has too much oil in it. Preferably tv tuner cleaner or something like that. If you can fit a pipe cleaner into the pinholes this is good, but not too likely for miniature tube sockets which have very small holes. Most poppy hissy amp I had just had dirty connections and a good thorough clean out always fixed the problem for me.

Good luck with your amp, you're lucky to even get a garage sale amp that works at all!;)
 
What a bargain!!!! :D

If its a really loud BANG it could be your B+ filter capacitors, the hi voltage can types. If you suspect this, then just change em, in fact its a good idea to replace all old capacitors with modern types, they tend to get leaky and fry things. However if its just some hiss and clicking sounds, its likely to be your preamp tubes have slightly corroded legs and there is some resistance... Easy fix (ie clean them!). Just watch out when you clean the glass of the tubes, the paint comes off real easy, and its a shame to lose those cool logos.

Welcome to the world of tubes! You can get great sound out of a tube amp, I was blown away by mine. For info, I go to google.com groups and search for whatever. You might be able to find a schematic somewhere online... Good luck!
 
Discharge the caps then resolder every joint.

If that doesnt help replace all the pots, zeners and electrolytic caps as these are the most common sources of noise and it is possible the tubes are also reaching the end of their life.

Although unlikely it is also possible that poor grounding of the heater elements is causing hum; however, i would say this is unlikely given that this is a commercial product.

Given the original price you paid even if you have to do all of the above, you will still have spent a comparatively small amount of money while you will also gain invaluable experience.
 
Thank you all for the help!! i'll be sure to do things in this order:

1. Clean everything first... (would alcohol be okay to use or does it really have to be that tv tuner stuff?)
2. Discharge all the caps and replace all the solders... I remember discharging caps in my electricity and electornics class but all i remember is him telling us not to stick our tounges on the caps. then he put the cap under a piece of paper and used a screw driver to connect the + -. It blew a hole through the paper... So could someone refresh my memory on how to properly do this... Thanks...
3. Change all the pots and sockets.

Thanks again for all your help!!
 
Yes alchohol works just fine, just try not to be sloppy.
A good tool to have is a small toothbrush or something with hard bristles to clean contacts and things. About discharging a cap, using a power resistor is the proper method to do this. Another way is to simply short the cap to ground but you get some pretty big sparks and arc welds this way with big caps. I once tried shorting out a 500000uF cap with a screwdriver and I had great trouble trying to pry it back off of the capacitor pins! It's also hard on hearing too. Generally, a 10k or 5k power resistor is good for cap discharging, it's nice to solder some test leads or clips to the resistor so you can easily make contact with the cap. Once you have let the resistor sit on the cap for a while you should then short it right out to make sure there is no more charge in the cap.;)
 
Do not use an alcohol spray on your controls. They will be best cleaned by the TV Tuner cleaner you can get at Radio Shack. It cleans and lubes. Wait a day after you do this before applying power or if you are impatient like me get a hair drier after it. Another weird but really good thing to do with old gear like this is to remove the bottom cover and bake the thing upside down in your stove at 150 to 200 degrees for an hour or so. Those old carbon resisters can often get back into specs if they are dried out. Upside down because you don't want any water vapor to get up into the transformers and then turn into water when it cools off and short the amp out. To clean your tubes pour a bit of Tarnex into a plastic bottle cap and stand the tube up in it for a minute. You want the tarnex to come about 3/4 the way up yhe pins. Keep it away from the glass. Clean the Tarnex off with a paper towel that has hot water on it and dry the pins off before putting them back into the amp. A good idea is to put the same tube back into the same socket so clean them one at a time. If you want to clean the chassis the best thing for cleaning where there are decals that say volume etc is to use the car wax in the orange bottle(can't remember the brand). You can clean circuit boards with mineral spirits and an old tooth brush. I clean chrome chassis with Mother's polish and then protect with the wax. My recommendation about solder joints is to use a magnifier and a probe and just put a bit of stress on the joint while looking through the lense for a close up view. Only resolder bad solder joints. If you just have a cheap iron from Radio Shack the least amount of time you have it stuck down in there the better because they don't have the heat to do it quickly and you stand a good chance of melting something you don't want to. If you don't remember about cleaning and tinning your tip before touching the solder joint ask. Bell made some great stuff. Enjoy!
 
Didn't say ya did. It is just that there are a lot of alcohol solvent sprays used for cleaning computer parts including dials and switches and I didn't want him to use one and strip his pots. These sprays are much more common than ones good for cleaning antique potentiometers. It had absolutly nothing to do with what you had posted and if you had read what I wrote in the way it was given you should have noticed that. The only thing I wrote that contradicted an earlier post was about resoldering every joint. I thought that was excessive especially if he doesn't have a solder station with the heat and tips to do the job quickly without causing other problems. Hopefully I stated that in a way as to not cause offence to AF. Checking the joints is important. And I didn't notice a single post on a variac and how to use it and figured it was too late for it so didn't say a thing. It is always important to find out what tools somebody has before telling them to start changing things if they are a newbie. We don't even know if he has a wire stripper. At least he knows enough about the danger of high voltage storage caps to avoid smoke coming out his ears. Anybody in on the start of the thread mention the fact that the tubes themselves might be in question? Nobody covers everything and some jump the gun before the basics are covered recommending replacing things that might well be perfectly fine. But truly my comment about using a spray on pots had nothing to do with rubbing alcohol and Q-tips.
 
And while you are in there replacing caps & resistors that have changed value, you should be sketching out the circuit as a reference. I start with a drawing of the tubes & their pinouts and all the stuff that should be there, like OPTs & power transformer. At 1st it may be baffling but you can learn a lot. Once you have done that, you can start excising the junk -- like tone controls -- and simplify the amp for better performance.

What are the tubes it uses? Model #?

dave
 
Thatch: I did mention that the tubes could cause this problem by being gassy or microphonic. Sorry I didn't get your statement the way you intended it, I do know that alchohol often strips carbon pots right out, but how often do you find a carbon pot in a tube amplifier?? They usually have just wirewound pots. Anyway, I get the point, alchohol is very bad for pots and one should use tv tuner cleaner, which is what I mentioned first anyway. Generally I use M.G. cleaners and sprays, can you get these at radio shack? I always got them at a local electronics shop with much better quality than radio shack.
 
Whew, i'm getting lotsa help!!

Well I've decided i'll go tomorrow to the radio shack to look for some tv tuner cleaner, that way i'm completely safe.

As for Tarnex, Thatch_Ear, I did some research and it seems like its something to clean instruments with, i had no clue on where to buy that stuff. I'll stand the tubes up in tv tuner cleaner like you said if thats okay.

I was planning to use a soft buffer on my rotary tool to buff away and polish the case, but things with words i'll do polish by hand. I figure if i change out the caps and resistors i won't really need to bake it.

One of my rooms in my house has been cleared out so that's going to be my "lab." Tomorrow on my list i'm going to get some tv tuner cleaner, a magnifer lamp, and some pipe cleaners. I have a 25 / 50 watt soldering iron i got from radio shack and flux. I'll make my cap de-charging device tomorrow out of a 5k resistor. Once i open it and make a list of all the resistors and caps i'll take pictures and let everyone know. then next on the list will be a multimeter, i'll slowing start building my lab as i keep learning.

I'll keep everyone updated!!!

Anyone know a good free easy photo program so i can make my pictures smaller, so i can put them on the web site? I don't need somthing to do super photo editing.

oh planet10
its a bell sound systems model 2122-c
it uses the following tubes:
5Y3GT
6V6GT (2 of them)
6SL7GT

Thanks!!
 
kpanda said:
its a bell sound systems model 2122-c
it uses the following tubes:
5Y3GT
6V6GT (2 of them)
6SL7GT

nice tube selection. 10-15W in PP. Now you just need a 2nd one and you will have a nice set of monoblocs. The OPT for the 6V6 is very close to that needed for EL84s so down the road that is also an option.

Some pictures for those who can't wait:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1362508171
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1362884103

dave