New HRM build

[ic-racer]

Thanks to UltraHookedOnPhonix for posting the pictures of his completed BM. It got me encourage to get working again.

I just ordered enough supplies to re-etch all new PC boards of the correct size.

I'm using kind of a hybrid technique. I see that UltraHookedOnPhonix just drew the patterns. I am using the iron-on technique and not worrying about a complete transfer and touching up things by hand. The first time I did it I worried a lot about not getting a complete transfer, but I have found out that the Sharpie pen works very well in filling in the blanks.

[ic-racer]

I found a place that would sell 8x10 samples for a buck a piece. I did a number of trials and the one with the red dot will be the one I will use for the main board.

[ChrisM]

Looks good.
Care to share your source?

[ic-racer]

Looks good.
Care to share your source?

https://samples.wilsonartcontract.com/

[jelle]

What is the name or item no for the one you picked?

[ChrisM]

Thanks ic-racer!

[tubedogsmith]

Isn't that stuff pretty brittle? Does it chip easy?

[ic-racer]

To recap the last year, the chassis I got has many pre-drilled holes that did not match up with my circuit board set. Rather than re-drill the chassis I went ahead and re-did the circuit board set.

In the last year I did get a dry-mount press, so I tired that instead of an iron, to transfer the Xerox to the copper board.

[amplifiednation]

Looks good.
Care to share your source?

https://samples.wilsonartcontract.com/

How thick is this? The laminate pieces I've seen have been VERY thin and flimsy.

[ic-racer]

Looks good.
Care to share your source?

https://samples.wilsonartcontract.com/

How thick is this? The laminate pieces I've seen have been VERY thin and flimsy.

Single piece is 0.9 mm. I also laminated two pieces together with epoxy to make a more robust piece and that one came out to be 2.0 mm.

[ic-racer]

After quite some time looking I finally tracked down a TF170 output transformer.

[jelle]

Oh, those are nice...NOS? I got one in my 183 clone. Sounds killer! Great iron.

[M Fowler]

What's the scoop on the TF170 output transformer I am not familiar with those?

Mark

[ic-racer]

Oh, those are nice...NOS? I got one in my 183 clone. Sounds killer! Great iron.

Yes, NOS.

If you notice the dates on this thread, this build is extending over 3 years. I wound up getting a better job, so not time for amp building. But I have more $$ for parts. So, I'm going to track down as much NOS stuff as I can find.

If anyone has any extra NOS components that fit this schematic I'll pay fair market value for them.

[ic-racer]

What's the scoop on the TF170 output transformer I am not familiar with those?

Mark

When I started this project a few years ago, the pictures I'm going by show a TF170 transformer clearly. In fact most of the EL34 HRM amps from the era I researched for this project (around #200 to #225) use the TF170. All these years I thought this was a common Marshall replacement item. So, when I went to actually buy one a few months ago, I was surprised to find it no longer available (though it is still shown on the http://www.magicparts.com/new/transformers.htm website). It also turns out the 183 amp circuit (which has recently become popular) also had a TF170. So I was kicking myself for not trying to locate the transformer three years ago . But it turns out I got lucky and found one anyway.

These transformers were discussed in some other threads (reproduced here in case I need to find the info again).

Couple of comments on that:

1. The story goes like this: Dumble ordered the TF-170s and the mounting tabs got all bent during shippping (has happened to me with just about every transformer I have ever ordered from anyone) -- the second half of the story is that, because of that, payment was never made on those parts... Anyway, it would explain why he would cut off the mounting tabs and use brackets instead.

2. Heard from people that the TF-170, when mounted as intended, would not fit in a Dumble combo with EVM-12L speaker. So, layout the OT down would shave off an inch off the vertical depth of the chassis... I only built heads, so I never ran into that problem.

Cheers,

Gil

The iron in this amp is called the TF series which was manufactured by TMI (transformer manufacturers incorporated). Magic Parts who use to be their distributor stopped selling these around 2002-03 when they replaced their TF line with that of another manufacturer (Marvel Electric Corp.).

TMI: www.tmitransformers.com/
Marvel Electric Corp.: http://www.marvelelectric.com/

TF-130: Twin Reverb PT
TF-170: Marshall 100W OT. Prim: 1730 Ohms, 20Hz-20kHz.
TF-155: Twin Reverb choke, 3 Henry, 90 Ohms DC res.

UltraHookedOnPhonix