Marshall 1930 Popular

[TIMBO]

Hi guys, The Marshall Popular MKII is now on the bench.
My local supplier has a bunch of 14GW8s on hand and so they have sourced a transformer with a 14.5v tap and 6.3v for the preamp valves.

[TIMBO]

Hi guys, New board done.
I changed the value of a couple of the capacitors as this is all I have.
I don't think it will change the tone/sound that much.

[TIMBO]

Hi guys, new board is in and wired up.




Updated schematic.
As you can see the OT is Ultra Linear, for no real reason other than this is the OT I had on hand.
So it's worth a try.

[shooter]

it's worth a try.

I like using UL, cathode biased, seems to create a secret sauce 

[TIMBO]

Thanks shooter, good to know.

[TIMBO]

Hi guys, The Popular II has kicked off well.
The reverb circuit was not connected as I was wanting to see what the original circuit noise level was like.
As stated before there is a background hum of an acceptable level, some buzz is present, but I'm hoping that will reduce once inside the cab.
Reverb circuit was connected, this did not add any additional hum.
Reverb is lush and plenty of it.

[TIMBO]

Hi guys, A mate was kind enough drop in to have a bash.
I think it does the Marshall thing well and does sound similar to the video clip in the first post.

Noise wise, it is more than acceptable at about half volume but is much nosier at full volume.
If this and was sold as a "cheap" practise amp half volume is more than enough volume for bedroom practise.

Tone pots have two rolls, tone of course with a good range between dark and light.
When turned to the bass sound is muddy and dull, turned to treble sound is bright and gainy. Me like it.
Roll the guitar back and cleans are great with a bit of hair. ( P90's in a LP JR)
Guitar at max and it's Marshall all the way.

Very happy with the end result.

[tubenit]

Wow!  That looks super nice!  Thanks for sharing the photos and info.

With respect, Tubenit

[DummyLoad]

nice work! :-) 


--pete

[Willabe]

WELL.................
WTF>>>>>>>>>
Found it.
Simply connected the reverb driver transformer to node"B" lush strong reverb and completely hum free.

Seems the B+ at node A wasn't clean enough to feed the verb driver stage?

The output stage being PP has noise cancellation built in, but the SE verb driver stage doesn't. 

Man, nice work sticking with it! 

[TIMBO]

Hi guys, Thought I'd have another go at getting the amp a bit quieter.
A few ideas have popped up over the last year or so...

I have added a voltage divider to simulate a volume pot to tame some of the ratty fizzy noise that is generated from the preamp.
I think what I have done may have helped.

[TIMBO]

Guy's this one needs to be finished.....
Some time injected into this has some good results..

I returned the circuit to the what I believed was the original Marshall circuit. (reverb disconnected)
The trem was a problem.
Finding the sweet spot of the 5k trimpot had the speaker flapping all over the place, but the trem was working.
I had played around with a voltage divider placed before the PI, and this somehow fixed the pumping speaker.
The sweet spot of the trim is about centre of the pot rotation.
I have since adjusted the voltage divider and it does not appear to affect the overall sound of the amp
I have replaced some of the coupling caps to be closer to the original circuit.
Fizz/hum has been reduced by adding a cap to ground at the junction of the 220k/100k plate resistors
There is a very faint background noise, I can live with.....



A new cab built with an old Celestion to give it a Marshall flavour

[TIMBO]

Cab completed

[uki]

Looks great !! Now put some skull knobs !!

[mresistor]

The cab looks great!