JTM50 Black Flag build, finally under way.

Ok, so I've been right through with the meter, everything showing good connections & everything correctly wired as it should be.WP_20190312_15_13_45_Smart.jpg
I have temporarily fitted a 32uf/32uf on the sidewall, just to check fitment. It is not soldered in & will be changed out for the 16uf/32uf (PI filter) when it arrivesWP_20190312_15_01_50_Smart.jpg
The earth lug is also on the sidewall. It will be the last thing to be connected (to the IEC sockets ground lug) before doing voltage checks etc.
So, now to install the electronic components. Cheers
 
Ok, I've just finished populating the board, not sure if a pic will be visible at the moment, but I'll try15727792241046337075558011317197.jpg
I'll clean any resin spatter & fingerprints off the board tomorrow. Hopefully the 16uf PI filter cap arrives early in the week so I can finish it off. Cheers
 
ivan H said:
Ok, I've just finished populating the board, not sure if a pic will be visible at the moment, but I'll tryView attachment 34017
I'll clean any resin spatter & fingerprints off the board tomorrow. Hopefully the 16uf PI filter cap arrives early in the week so I can finish it off. Cheers
Click to expand...

It's like looking at the present past if that makes sense. That's an awesome amp you've got go'n on there.
 
67plexi said:
Great job most don't have a clue whats involved in just sourcing the correct parts and world wide shipping expense.
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Yes... That's why some of these hand-built amps cost so much money. In my project, I'm saving a bit of money because I already have the power and output trannies ($$$$$), the 12" speaker ($$$), the 3 preamp tubes and 2 power tubes ($$), the reverb tank ($), and a couple of odds and ends ($). Even though I've sourced some semi-inexpensive parts to complete the new chassis, I'm still into this at the tune of over $350. This does not include the price of a new cabinet that I'm going to need... there's another $250 to $350 that I will be spending!

If I needed to buy the rest of the following stuff, it would break down like this: A pair of trannies for my amp could cost from $150 to $350. The speaker I already have and reusing is $120. A semi-cheap set of tubes would be about $70. Reverb tank is about $25. Other parts I already had is about another $25 worth. So theoretically, my 15 watt amp project could cost a minimum of $990, and up to $1290. At least I have FREE labor... :rolleyes2:

Also, a lot of the parts that Ivan has sourced, are much more rarer and much more expensive compared to my build. My conservative estimate for Ivan's parts is, add another 20% to the totals above! And... What's professional labor worth?
 
Thanks for the kind words guys, much appreciated. Sourcing NOS components can be time consuming & international shipping can be expensive. Waiting for delivery can be frustrating. The PI filter cap didn't arrive today either.
Anyway, I fitted the earth wire from the IEC socket to chassis sidewall IMG_20191104_111621.jpg
It reads 0.2 ohm from the prong in the socket to chassis, so easily meets standards. I then put a 2A Slow blow main fuse in & did all AC checks, all good. Checking the negative bias voltage shows a range of adjustment of -40V ~ -56V. This is with a 150k AC dropper resistor. This may need to be increase (180k ~ 220k) in order to get the EL34's to bias correctly. Speaking of tubes, I have a full compliment of NOS Blackburn Mullard valves to go into the ampIMG_20191104_184756.jpg
The EL34's are Philips Miniwatt branded xf2 (single halo) Mullard's with matching date codes, very closely matched plate current & transconductance. The Valvo branded f32 GZ34 was in my '68 50 watt amp, but as only a few of the '68 amps were tube rectified vs most of the black flag amps, I removed it in favour of a solid state rectifier (& higher filtering). The GZ34 has a few hundred hours on it, but that's nothing for a Mullard, which should outlast me in this amp & it's still outputing 100%. I have four (RTC branded) 163 series Mullard 12AX7's to choose from (all with Blackburn '74 codes). Many think that choosing for V1 is the most important, but for me, finding the one that performs best in the V3 PI position is (shooting for a plate differential voltage of 7.2 or 7.3 volts). Then I'll choose V1 & V2. Now, if only the PI filter would arrive. Filters will be conditioned by current limiting (100k resistor). So, until the filter cap arrives I've put the chassis into the headcabWP_20190313_10_45_26_Smart.jpg
Note the "Loudness 1 & 2" rather than "Volume 1 & 2". Also the "Black Flag" front panel. I don't usually bother with things like this but Robert at Valvestorm had one so I thought why notWP_20190313_10_46_13_Smart.jpg Cheers
 
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Robert Herndon said:
My mind works strangely....im already thinking Black Flag, 50 watt 4x10 Combo...

Im almost grateful i dont know how to do this kind of work.

This rabbit hole appears deep...
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The combo version was the model 1962, or 1962T for the tremelo model, though it was a 2x12. Back then you in the early days Marshall would do one off's, which was how the combo amps came about (Clapton's bluesbreaker amp, he wanted it to fit into the boot, or trunk of his car), so I suppose a 4x10 would've been possible. I can understand you wanting a 4x10 too, a buddy has a G10 loaded (Marshall) 4x10 & it is a fantastic sounding cab. Cheers
 
ivan H said:
The combo version was the model 1962, or 1962T for the tremelo model, though it was a 2x12. Back then you in the early days Marshall would do one off's, which was how the combo amps came about (Clapton's bluesbreaker amp, he wanted it to fit into the boot, or trunk of his car), so I suppose a 4x10 would've been possible. I can understand you wanting a 4x10 too, a buddy has a G10 loaded (Marshall) 4x10 & it is a fantastic sounding cab. Cheers
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If i ever have the $$$$ i would pay you to build me a one-off
 
Outstanding!!
I am really enjoying this ride.
It occurs to me I like these tube pics almost as much as boob pics.
I did say almost.

This thread is what motivated me to get started on another build i had in mind but had not put into action.
Got the iron on order and 3 NOS Sylvania 12AU7 on the way.
This micro uses both triodes of 1 12AU7 as push/pull power section.
Still mulling a scratch chassis or $50. premade Princeton Reverb chassis.
 
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Marshall did make a 4 x 10" combo called a model # 1961 built in 1964 through 1965

www.truetonemusic.com

The Elusive, Vintage, Marshall Super Tremolo

***CALL FOR PRICE*** Whenever a discussion turns to how the circuit for the first JTM45 was lifted nearly point for point from that of Fender’s 5F6-A Bassman combo, it seems there’s always a caveat about how it ended up sounding slightly different as a head through a closed-back 4x12" cab. Oh...
www.truetonemusic.com
 
67plexi said:
Marshall did make a 4 x 10" combo called a model # 1961 built in 1964 through 1965

www.truetonemusic.com

The Elusive, Vintage, Marshall Super Tremolo

***CALL FOR PRICE*** Whenever a discussion turns to how the circuit for the first JTM45 was lifted nearly point for point from that of Fender’s 5F6-A Bassman combo, it seems there’s always a caveat about how it ended up sounding slightly different as a head through a closed-back 4x12" cab. Oh...
www.truetonemusic.com
Click to expand...

OMG!!!!!!!
 
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