'69 Drip-Edge Bandmaster TFL5005D

[Tone Meister]

A friend bought one of these for almost nothing because it wouldn't power on, then brought it by for me to check out. Traced the short to the bias circuit, secondary produces ~400vDC on the LBL. Tested the OT and it's still good, so this should be a straight forward service/repair situation, except I have never seen a Bandmaster TFL5005D before and want to run it by the pros before jumping in feet first. One thing that struck me as odd was the power tube arrangement.

Main power switch was changed at some point as well as the 100 ohm center tap resistors for the heater circuit. Lots of goop inside in several places.

Here is the plan with amp on light bulb limiter and auto-transformer:

1. Repair bias circuit to remove secondary shorting condition, stabilize amp, THEN:
2. Change every electrolytic cap in the amp
3. Install grounded power cord, remove death cap, wire to current standards
4. Streamline the bias circuit, wire to BF convention

For those with experience with this specific model, I'd appreciate any caveats, gotcha warnings, and solid advice you might have before I move forward. I'll likely start the repairs in a week or two, so in the meantime I'll be seeking information.

EDIT TO ADD: The attached schematic shows a much simpler bias arrangement and only two 6L6GC power tubes, yet it is labeled TFL5005D. Anyone have any information that would clear that up?

EVEN MORE CONFUSED NOW: The printing at the speaker output reads 40 watts! But there are clearly four 6L6GC power tubes, and it doesn't indicate minimum impedance load

OK, does anyone here know what I have here?

[xtian]

You’ve got the right idea. Standard stuff. Is this the head with the extra tall cabinet? I installed a pair of 8” Jensen speakers in one, to make a super cute 2x8 combo.

[Tone Meister]

You’ve got the right idea. Standard stuff. Is this the head with the extra tall cabinet? I installed a pair of 8” Jensen speakers in one, to make a super cute 2x8 combo.

Yes, the head cabinet is 13" tall from top of the handle to the bottom of the feet

[alexradium]

i would keep the bias balance pot,and add a trimmer for global voltage setting,best of both worlds.

[pdf64]

Schematic link?
Whatever, it looks to have been heavily modded, with 2 extra power tubes added, HT caps and a messy looking rectifier. Lord knows what else.
I think that the work it needs goes way beyond what would reasonably described as regular maintenance / service.
More like a major rebuild.
I suggest to strip it back to the chassis, work out exactly what the PT and OT part #s are that are in there (eg have they been 'upgraded' to TR types), then from that, decide which way to go with it.
If you're charging for your time, making a proper job of it will cost a lot, perhaps way more than your friend thinks worthwhile, so to avoid souring a friendship / being taken for a mug, consider declining the job.
If you want to do the work, maybe offer to buy it, then at least you'll get any profit resulting from your work.

[bob p]

The iron set is doing to define what you can do with the amp. I agree that Identifying the iron is the first step.

I hate to see amps come in that are cobbled like this. I hate to repair other peoples' home cooking. I have a special rate for that.

If I had to guess, the goop everywhere was a lame effort at stomping out vibrations.

[Tone Meister]

Schematic link?
Whatever, it looks to have been heavily modded, with 2 extra power tubes added, HT caps and a messy looking rectifier. Lord knows what else.
I think that the work it needs goes way beyond what would reasonably described as regular maintenance / service.
More like a major rebuild.
I suggest to strip it back to the chassis, work out exactly what the PT and OT part #s are that are in there (eg have they been 'upgraded' to TR types), then from that, decide which way to go with it.
If you're charging for your time, making a proper job of it will cost a lot, perhaps way more than your friend thinks worthwhile, so to avoid souring a friendship / being taken for a mug, consider declining the job.
If you want to do the work, maybe offer to buy it, then at least you'll get any profit resulting from your work.

Thanks Pete, for the candid reply. Schematic is linked in the first post, just under the bottom photograph. I'll post it again here to be sure it can be easily found

[pdf64]

Thanks Pete, for the candid reply. Schematic is linked in the first post, just under the bottom photograph. I'll post it again here to be sure it can be easily found

Oh yeah, duh
So the end octal socket was originally for the rectifier.

[mozz]

Some dripedges i have seen can usually be any of 3 schematics and partial schematics in-between.

[Tone Meister]

... So the end octal socket was originally for the rectifier.

Yep. I'm trying to wrap my mind around how someone could put all that work into such an extensive mod and leave all those potentially volatile parts in place? Of course, that mod could have taken place years ago when said parts were much fresher.

The work was performed by Andre Audio-Tronics in NY, NY. They are still in business with the same phone number and also have a presence in Canada. Seems to me like it would have been cheaper and much simpler to trade her in on a Dual Showman and call it a day.

Got me scratchin' my head, though, for sure.

[The Dude]

......I suggest to strip it back to the chassis, work out exactly what the PT and OT part #s are that are in there (eg have they been 'upgraded' to TR types), then from that, decide which way to go with it......

Agree. Looking at the kludge work there, it's reasonable to assume that the transformers might be original and not up to the task of 2 additional output tubes. The gooped in caps are a quandary. Makes me wonder what's going on in the doghouse? You should have a look there, too. If it were mine, I'd strip out all the mods and put it back to original (assuming the transformers are original). Also, does the PT have a winding for a tube rectifier filament? Might not be there if the PT has been changed.

[Tone Meister]

Iron is as follows:

PT - KO22756, power transformer for Twin/Dual Showman (dated 1973)
OT - 022897, output transformer from Twin/Dual Showman (dated 1973)
RT - 022921, standard reverb driver (dated 1969)
Choke - 022699, standard 90 mA choke (dated 1969)

[Tone Meister]

Agree. Looking at the kludge work there, it's reasonable to assume that the transformers might be original and not up to the task of 2 additional output tubes. If it were mine, I'd strip out all the mods and put it back to original (assuming the transformers are original).

PT was changed to a circa 1973 Twin/Dual Showman KO22756

The gooped in caps are a quandary. Makes me wonder what's going on in the doghouse? You should have a look there, too.

Doghouse caps are original Mallorys that have never been touched

Also, does the PT have a winding for a tube rectifier filament? Might not be there if the PT has been changed.

No filament winding for tube rectifier.

Seems like a valid mod, even if is taking the long way around to building a Dual Showman. I might try repairing the bias feed and see what happens with her on the LBL. Can't hurt, I suppose.

[The Dude]

So it appears the iron was changed. Somebody did a lot of work for little gain, IMO. Without a filament winding for it, no tube rectifier possible, which isn't a big deal. You may as well leave the extra output tubes. I would clean up the filter cap situation, though. I'm not sure why they did that- put caps inside the chassis. I'd just use doghouse caps like every other Fender of the era and get rid of the gooped up mess.

[Tone Meister]

So it appears the iron was changed. Somebody did a lot of work for little gain, IMO. Without a filament winding for it, no tube rectifier possible, which isn't a big deal. You may as well leave the extra output tubes. I would clean up the filter cap situation, though. I'm not sure why they did that- put caps inside the chassis. I'd just use doghouse caps like every other Fender of the era and get rid of the gooped up mess.

That's what I was thinking initially. Right now there are two 70 uF and three 20 uF in the doghouse, which is exactly what every one of the silverface Showmans had. First order of business is to repair the bias feed and see if it'll stabilize and pass signal, then I'll worry about the next step, if any. If I get that far, I'll up those values in the doghouse to 2 x 100 uF and 3 x 22 uF which will be adequate.