I'm feeling like the Maytag Repair Man

[Platefire]

Sure is boaring! All my amps are working Great. I'm not really complaining but I attribute it to everthing I've learned from this forum helps me head a lot of problems off at the pass. Thanks, Platefire

[jeff]

If you're bored, try throwing an amp down the stairs. Maybe you'll knock something loose and have something to do.

[bigsbybender]

I'm busier than ever! I don't have time to work on my own.

This week on the Tube amp front, I just finished a Mid-60's Sears Silvertone 1484 "Twin Twelve". Waiting in the wings are a 59' 5F1 Champ, a 61' Gibson GA-5, a 1964 Fender Twin Reverb, and some Boutique amp head (Circuit Looks Fender-y at first glance.) I just got a call today about a Magnatone amp where his pitch-bending Vibrato isn't working. I'm pretty excited about that one.

j.

[jeff]

How'd you check the 1484's bias? My brother gave me one of those and it looks pretty tight in there, kinda like playing "operation", don't touch the sides or your nose will light up.

 Also they take the bias off a winding and there is no adjustment, or even curcuit to make an adjustment by changing resistors. The voltage comes right off the tap and what you get is what you get. Did you install a pot or circuit? I've heard tell about needing to add a voltage doubler to raise the bias voltage because the tap's voltage is too low. Is that neccessary?

[bigsbybender]

I left it as-is.  The amp sounded very nice so I didn't bother. It is tight in there, but surprisingly cleanly manufactured. This Sears cheapy is better made than Gibson amps of the same vintage (with the exception of the reverb tank).

By the look of it, you'd likely have to use a voltage doubler to have any large range of adjustability. If you're serious about doing that, it wouldn't hurt to find a pre-made PCB board setup so you don't have to get wildly creative stuffing all the components in there.

I figured that it was a cheap amp and there is some mojo in the cheapness. It was for a customer who deals in vintage gear so I needed to keep the changes to a minimum and the repair cost low so he can make a profit when he puts it on the market.


j.

[jeff]

That's the way they were sold as-is. I did throw tubes in and try it out but I stopped using it because I'm paraniod about bias.

You're right about the reverb. My theory is, among other things, as you turn the reverb up you're sending more to the tank driving it harder. The reverb knob is really a dwell not a volume. I always wanted to rewire it so you're not driving it harded but add a stage to after the tank to get more volume. Yeah it's crappy but it gets crappier as you turn it up. May sound better driven softer but have the output amplified. Probally never sound great but maybe better.

Seems simple enough to try out. Disconnect the wire at the switch(back of the reverb pot) and connect to the hot of a guitar cable. Plug that into the input of CH1, use the reverb as the dwell and the volume of CH 1 as reverb, plus you get a reverb tone knob.

Maybe I ought to dust that thing off.

[Ritchie200]

it looks pretty tight in there, kinda like playing "operation", don't touch the sides or your nose will light up.

 

Jim

[Platefire]

Yeah, I would really love some tube repair work and even left an information page at several music shops but all I get is calls to repair solid state stuff. I guy called me this week about his SS PA head. Even if I got a call on a Hybred amp, I would go for that but not yet. If I got a call on an old fender, Gibson or Magnatone amp, I would probably go nuts! Platefire

[TubeGeek]

I wish I could send some work your way...I often have so many amps coming in for repair that I seldom have time to work on my own projects.

[bigsbybender]

I'm just now getting back to tube amps. People dumped solid state on me for the first 5 months of the year, I really hate working on SS and it's not worth it but when it was slow I couldn't turn down work. Now it seems that since I fixed a load of SS gear, the newer customers are trusting me with their beloved tube amps. The last TV/Radio repair shop in this town closed last year, his longtime customers are trickling my way.


j.

[Platefire]

I've been tempted to take SS stuff for repair but I live in the back woods and to make it worth my while I would have to get them to bring it to me from far away and then come pick it up when it was done. To have them travel all that far and not even know if I can do them any good not being familiar with SS stuff, I just bow out. Most of them are calling from like 50 miles away. I know without a doubt with my experiance and the help of this forum, I could get to the bottom of any problem with a turret board/eyelet board tube amp but SS is a big ???  If I lived in a town with easy access, I would probably tell them just to bring it by to see if I could do something with it. I wouldn't mind trying to fix them but they might get kind of upset driving 120 mile round trip with no results!  Platefire

[bigsbybender]

I just picked up two old amps that belong to the same guy who wants them gone through, it's pair of fun little repairs. A 1959 5F1 Champ and a ~1960 Gibson GA-5 Skylark. These are virtually the same amp. All in all they sound very similar, right now the Champ edges it out for better tone, but the Gibson has never had maintenance and has a little bit cheaper speaker than the champ (both original). Sadly someone in the past removed all of the tweed from the champ.

I hooked them up with an AB-Y switch to compare them. Astron caps in both, and they are bulging, so they'll have to go.


j.

[Platefire]

Shame on you for thrity minuets or even longer! Some poeple get to have all the fun.   

Man! I would be some excited if some one brought something like that to me---so enjoy!
Please post what you finally decided to change out and how much improvement it made.

The GA-40 Les Paul amp I once owned was completely stripped of its tweed. So that was my first experiance installing tweed. Platefire

[Platefire]

 The Tide Turned today!!!    Got a call from a guy with a 66 Vibrolux (not a RI) and a 1981 Marshall JCM 800 Head that he want me work on. Basicly wanting a tune up on both amps and mentioned something about a effects loop mod---but I'll probably highly recomend against that as not to degrade his vintage equipment. So I'm glad to get some some old amps to work on. Platefire

[TubeGeek]

Nice jobs!  I'd have fun with those too.  I just sent home a silverface 69 super reverb that was overhauled and a jcm 2000 head in for post-tour checkup tonight.  Those were fun, I love the old fender's.

Next job up for me is a build...65 twin reverb! Oh yeah.  I drive to the Canada/USA border in the morning to pick up all the parts.  It saves me $400 in border brokerage fees.   At least I get a nice drive down the Alberta prairies to a place in Montana called Sweetgrass.  How can I go wrong with that?

Anyhow, I'm rambling...have fun with your jobs, keep us posted and glad the tide turned.

[bigsbybender]

I note that I've sold a lot of stuff to Sweetgrass, and the addresses are PO boxes and Storage Facilities. You must not be the only guy that does this.

[TubeGeek]

Yeah it is common to do that.  Sweetgrass is a tiny town with a bunch of storage and warehouse space.  It is quite a bit of savings if we go pick it up and take it across the border ourselves.  I literally saved $300 on this order.  Its the darn brokerage fees that are avoided.