Bluesmaster HRM question:

[martin manning]

The Bassman RI would produce a pretty high B+1 voltage, 490V on the '59 Bassman reissue schematic. You could use it and drop the PI and preamp voltages down as you have done before.

[bepone]

Looked it up and it’s 374-0-374vac with 6.9vac heater wind and 57.6vac bias supply (unloaded voltages). It’s a little higher than the BF spec Bassman, but it’s cheap. Too much voltage or can it be made to work?

you can add tube rectifier GZ34 to eat that voltage

[Raoul Duke]

The Bassman RI would produce a pretty high B+1 voltage, 490V on the '59 Bassman reissue schematic. You could use it and drop the PI and preamp voltages down as you have done before.

That’s what I was thinking, but I’m concerned about the 2nd & 3rd order (unforeseen) effects. You once gave me solid advice about getting the correct spec iron if at all possible - I should probably just stick to that. I’m always swayed by saving a buck - but “buy right; buy once” seems to apply maybe? I don’t mean to be “wishy-washy” - just thought past being a cheapskate, lol.

That OT look like the solution I think it is?


bepone - understood, but I’d rather stick with the SS rectifier for this I think. Seems truer to the circuit. BTW - Really enjoyed reading about your 183 derivatives. Very informative to follow your process with these.

I’ll probably start ordering the small parts this week, just trying to figure out the V1 resistor material. I can see with the amount of gain in this circuit that the 220k could likely be metal film; but I’m trying to figure out what most folks used as well as finding pictures of actual Dumble BMs.

Thank you both!

[martin manning]

I have no idea why Fender wanted such high voltage on the reissue Bassman. The original 5F6-A voltage was shown at 450V.

That OT look like the solution I think it is?

Should be fine. I think you'd be good with the Black Bassman PT, or maybe Hammond 290DX.

...just trying to figure out the V1 resistor material.

Dale's for the plate loads, CF or MF for the rest. I'm a resistor heretic, though.

[Raoul Duke]

Ha! I’ve seen that in the threads I’ve read, lol.

I understand the attraction to using the same materials as the master - and I also understand the reality that a lot of that stuff ain’t being’ made anymore - so we need to find the modern equivalent and concentrate on technique (i.e. layout, lead dress etc).

I like to think I’m somewhere in the middle. If the original-type stuff is available and in good condition at a reasonable price - I’d probably use it. If not - pick a modern sub and move forward. All the Pihers and Iskras and Q-lines in the world aren’t going to make up for my lack of knowledge, lol.

It’s all good. I love reading here and everyone has a valuable experience to share. So much to learn in just about every thread!

Thanks Martin!

[didit]

I'm a resistor heretic, though.

Beg to differ, asserting that skeptical schismatic would a closer positional descriptive.

..

[Raoul Duke]

Just throwing some stuff in my Mouser cart and found that they won’t have the trusty 166F12C 12v transformer for about a month. Plugged the spec’s into the search tool and came back with the Triad F-216X. Everything matches up except that the Triad is not CT’d. Does that rule this model out or is it a suitable replacement? In my 102 the CT wasn’t used and the BM 12v system looks the same.

Here’s the data sheet:

F_216X-780869.pdf

Any guidance is appreciated!

[ijedouglas]

Just throwing some stuff in my Mouser cart and found that they won’t have the trusty 166F12C 12v transformer for about a month. Plugged the spec’s into the search tool and came back with the Triad F-216X. Everything matches up except that the Triad is not CT’d. Does that rule this model out or is it a suitable replacement? In my 102 the CT wasn’t used and the BM 12v system looks the same.

Here’s the data sheet:
F_216X-780869.pdf

Any guidance is appreciated!

Should be fine

[martin manning]

Cheap, too!

[Raoul Duke]

Thanks Ian, very much appreciated!

I figured how important can the CT be in this application if it’s trimmed and capped - but just wanted to be sure I wasn’t missing something.

Thanks again!

[Raoul Duke]

Cheap, too!

Perfect for a cheap skate like me, lol!

[bepone]

bepone - understood, but I’d rather stick with the SS rectifier for this I think. Seems truer to the circuit. BTW - Really enjoyed reading about your 183 derivatives. Very informative to follow your process with these.

thanks, will be update in the theme soon, mounting vintage Carsbro transformers on one, can't wait for the final result!

if you want SS but reduce some voltage you can put also 100R 20W resistor after the diodes , before the first electrolytic cap.. will be fine

[Raoul Duke]

I have no idea why Fender wanted such high voltage on the reissue Bassman. The original 5F6-A voltage was shown at 450V.

That OT look like the solution I think it is?

Should be fine. I think you'd be good with the Black Bassman PT, or maybe Hammond 290DX.

...just trying to figure out the V1 resistor material.

Dale's for the plate loads, CF or MF for the rest. I'm a resistor heretic, though.

Thanks bepone! Great tip I’ll keep for future use!

Martin, is there any advantage to the slightly lower voltage 290DX in the BM-type circuit?

Got the Dales for the plate loads as prescribed; I think I’m hung up on all the different color resistors in the layout - which drove me to look at pictures. I see some builds and originals with MF on the tube sockets, some with CF; most with a mix of the two. I’ve seen one or two with Dale 22k on V1A as well.

Am I too deep in these weeds? Should I just choose some good quality CF and keep moving?

[martin manning]

Re the voltages, most important is to get the V1 plates into line. As I said, I don't have any direct BM experience, and there aren't any voltages listed on the layout. The TF-130 PT was a Fender Twin replacement, so you should shoot for 440-450V B+1.

I think I’m hung up on all the different color resistors in the layout...

On the resistor types, I believe the cerulean and azure blue in the layout are MF, yellow ochre are CF, and the raw sienna are Dale RN65 MF. I think either all MF or all CF (except for the plates) would be fine too, in spite of what some people say about MF being over-bright or "sterile" sounding.

[Raoul Duke]

Super helpful, thanks Martin!

I wonder how the layout’s dropping string values would interact with a Bassman spec PT? I realize the PI is different and that plays a part. This will be an interesting build. I see lots of learning opportunities. Doing the research and trying to gain more understanding before building combined with my two previous projects has me feeling more comfortable with the whole process.

That and the incomparable help and tutelage I receive here. Very grateful for all the patience and help guys!

Almost time for a new build thread…