Marshall 1974X combo

[M Fowler]

Yeah it is but I think I already went down that rabbit hole once and not sure how that 820K got in there.

I've gone through each component so many times the build is looking sad.

Will change that out and see what happens maybe the amp will self destruct.

Mark

[M Fowler]

sonicmojo and Slucky thanks a lot that worked, I must have put another 820K back in the same spot because I changed that resistor once already.

This time I got tremolo and correct volume at full volume.

Thank you guys.

[M Fowler]

Slucky on the 1st 1974x combo I was working on I ended up having to put a 120pf cap parallel to the 100k B+ dropping string resistor to stop oscillation.

That amp is now working fine too. Easy to build my ass!

Thanks guys.

Mark

[martin manning]

Which resistor is that Mark? Do you mean V1's plate load?

[sluckey]

The original 1974 is very notorious for aggravating tremolo problems. I think it's just a poor design. There were hundreds of posts at 18watt.com about this. Plenty of band aids that worked for one guy but not for another. The fix I show on my schematic is just another example of a band aid for my annoying "tick".

My Supro has a very similar tremolo but the trem triode is inside another bottle. No problems. I've often wondered if having the high signal level trem triode in the same bottle as the low level preamp triode is the cause. Never lost any sleep though.

[M Fowler]

The plate load for V3 100k.

The sound I was hearing was an oscillation like a radio tuning between stations but I look over Sluckey's schematic and decided to try that cap parallel to the 100k plate resistor and it worked.
Noise stopped and tremolo sounded very good. Foot switch worked and after testing I'm in the process of building a back board to mount my chassis into cabinet. Not sure where the original back board went to on this cabinet it had a rough cut bare plywood board with it and requires some trimming to use.

Mark

[M Fowler]

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Received the Cannibus Rex Eminence speaker from owner and loaded speaker and amp into Peter Mather cabinet, looking sweet and sounds so delicious.

Mark

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[Colossal]

Very, very nice Mark. I am starting another 18W.

[M Fowler]

Dave,

Do you have as much problems as I do building these 18w tremolo amps.

Took so long to figure out problems and I had the Marshall 1974x amp sitting right next to the bench to copy.
Marshall really wires their 1974x nice.

Mark

[Colossal]

Dave,

Do you have as much problems as I do building these 18w tremolo amps.

Took so long to figure out problems and I had the Marshall 1974x amp sitting right next to the bench to copy.
Marshall really wires their 1974x nice.

Mark

Yes, the HW'd 1974s are pretty. No Mark, I have no issues with the tremolo amps because I don't build the trem channel This next amp will be a parallel Normal channel with Vol and Tone and then a Cascaded channel with Gain, Vol and Tone. I have a Mather 18W cab for it. Should be fun. I sold a Lite IIb a couple of weeks ago.

[M Fowler]

Glad your having fun with some sales and build brother.

I still have my loud as heck Lite IIB built from Hammond AO-35 chassis/original PT and OT.