Oh no! It's an intermittent fault!

[geoff 1965]

i agree, it's a simple mod which you can easily return to stock if you want to. here's a good layout showing single/parallel with cliff jacks and side view to easily see the wiring

BN_LITE2B_LAYOUT_CT_TRANS_FINAL_REV1.6.jpg

[Daviedawg]

Thanks Geoff. I was looking for a simple diagram like that.

Dd

[brettl-s]

Excellent diagram, might give that a try. Many thanks from a newbie to all who contributed.

Cheers, Brett

[geoff 1965]

thank's for posting the pics Brett,
the marshall schematic does'nt show PT or circuit voltages and one thing that's been bugging me is the 91R biasing on the el84's on these "reissue" amps! i can see what they have done using a lower 275-0-275 HT with the ez81.

[colossal]

thank's for posting the pics Brett,
the marshall schematic does'nt show PT or circuit voltages and one thing that's been bugging me is the 91R biasing on the el84's on these "reissue" amps! i can see what they have done using a lower 275-0-275 HT with the ez81.

Surely that 91R has to be a typo. 120R is hot. Around here, we typically use 150R. Also interesting to note that they show 56k for the PI tail resistor on the PI, not 47k.

[geoff 1965]

it's not a typo colossal!
and that's what i was puzzled with,but they will be bringing the dissipation up from the lower B+ i think.
have a zoom in on the pic it's a 91R C10 wirewound!

[Daviedawg]

It would be interesting to have a set of voltages from that amp to see how it all comes together.

Dd

[colossal]

it's not a typo colossal!
and that's what i was puzzled with,but they will be bringing the dissipation up from the lower B+ i think.
have a zoom in on the pic it's a 91R C10 wirewound!

Well ok! (Tugs at collar)...yikes, they really had to change the voltages then. When you think about it, early Voxes used 50 and 68R for four EL84s and they were often biased to 130% of max dissipation. Changing the voltages in these 18W amps changes their character and response. I am pretty sure the first 1974x reissue ran afoul of power transformer failures early on as well.

It would be interesting to have a set of voltages from that amp to see how it all comes together.

Dd

Yes it would. Everything would make a lot more sense. Nothing more useless than a schematic without voltages. Here's all the ingredients for a cake but no oven temp

[geoff 1965]

yeah i'd love to know the voltages on those el84's!
they are probably making use of 275-0-275 PT thats used in some of their other amps to keep cost down?

[crgfrench]

Nothing more useless than a schematic without voltages. Here's all the ingredients for a cake but no oven temp

That's the most colossal analogy I read all week!