The Steel Guitar Forum

1. I have an original Fender 4x10 Bassman amp that I purchased back in 1985. It has been a wonderful sounding amp for guitar and reasonably reliable. About 6 months ago it started making sounds every time I hit a C note. So I took it into our city's main amp guru and after about 3 days I got it back and he advised that it was just a loose connection. However on my first gig back with it I noticed that it had considerably less gain. Where I used to run the amp volume on 4 I had to run it on 6-7. The amp guru said that its probably something worn out. Before I go spending more money on the guru I was wondering is there anything obvious that would cause such a reduction in gain (tubes etc)that I could look into?

2. For a steel amp I have been using LTD 400 since the mid 70's and it has been amazingly reliable. In 1980 it blew up on stage. I took it to the regional
Peavey distributor and they fixed it in one day saying that the amp was so powerful that it shook the connections loose and they used speaker glue to secure everything. Last August the amp blew up again and our local guru stated that it was a loose connection. I mentioned the speaker glue story and he had never heard of this. I was wondering if anyone else has had the same experience as I have become somewhat gun shy using the amp without a backup.

Beware of gurus

Amen. A lack of reliable gurus forced me to learn to work on my own amps.

You need to be aware that if you have a nice, sweet, hot preamp tube in your V1 position... and someone swaps it out with a normal, newer, crappier tube... you will have been ripped off... and could have the symptoms you describe.

So
1.) know your tube amp doctor, and
2.) know what you're running in all holes.

To prevent valuable tubes from being "hijacked", mark all your tubes with a dot of paint. Then tell the serviceman that if they replace any tubes, you want the old ones back.

What you are hearing here is worth listening too. I had a real sweet Mesa Boogie tube amp. All original tubes. I had some work done on it and it came back with some different tubes and now sounds like crap.
Anytime I will take an amp to get worked on I will mark the tubes and let them know it.I don't think these eastern European tubes are the same.

Also, be aware that the '50's Bassmans (Bassmen?) had a lower-gain tube in V1 as stock... a 12AY7 instead of a 12AX7. If the tubes get swapped around in there you could end up with less gain in your V1 position if you were running a 12AX7 in there before. The amp gets pretty dirty with a 12AX7 there... so it might just pay to check what's in there now.

Unless you really know your amp tech, it is a good idea to make a hidden mark on anything valuable that could be removed from a guitar or amp, like pickups (guitar) or pots/tubes/speakers on an amp. If dealing with someone I didn't know well, I might even sub out a nice set of old American tubes with tubes that worked OK but I didn't care about. However subbing out power tubes is an issue if the tech is going to rebias the amp.

With all that said - the stock 1st preamp tube in an original narrow-panel tweed Bassman (5E6 through 5F6A) is a 12AY7. If you had a higher-gain 12AX7 in there originally and the tech subbed a 12AY7, that would produce the effect you're describing. I regularly use a 5E6 '57 Bassman, and I prefer the stock 12AY7. So someone making that swap isn't necessarily trying to rip a client off - that's simply the correct tube, although some people do prefer the 12AX7. But a tech should not do this without telling you AND also returning the original tube(s).

I also have had an LTD 400, in my case for the last 13-14 years. I have had connections come loose in more than one Peavey steel amp, and I just opened up the amp and re-seated the connection. The molex reverb connectors are famous for this. These are very powerful amps, no doubt, and I suppose that stabilizing the connection with some type of adhesive may make sense in some cases. But I don't know that this is always necessary and I wouldn't conclude that the tech is incompetent simply because he didn't do this.

I finally had a chance to pull the amp out and check the tubes. All three preamp tubes are 12Ax7's. They appear to be the tubes I put in there probably 8-9 years ago( 2 Mesa's and 1 Gt). I suppose the next step is to try some new tubes although it seems strange to me that the amp was doing fine until this last visit to the tech shop.
Bye the way thanks everyone for your input.

Since they're all the same you can try swapping them around and see if you notice any improvement... it pays to keep a good spare around for swapping in, also.

I did a whole bunch of swapping today even with some old Chinese tubes I had in the amp years ago. There were some slight tonal differences but the gain stayed quite consistent. Oh well the amp is totally useable with enough volume to do the gigs that I do. But it sure would be nice to have it running the way I'm used to it running.

sounds like your original problem is probably in the power supply. That c note was the resonant freq. equal to were the power supply was failing. i would shotgun all the caps in the power supply right away. This fixes about 90% of all those weird unexplainable problems that suddenly pop up out of nowhere. The original caps in any electronic gear will eventually dry out and consequently slowly kill the supply voltages going to all the tubes or finals.

Thanks Tom. I had the caps replaced about 15 years ago and I store my amp beside my furnace. Probably not a good idea. I will take the amp in to my guru and see what happens.