Just drew out a schematic for my JTM45 build

[NZaudio]

very tidy, very tidy. Good work
Regarding the 1k or 1k5 resistors in series t the grids, they are really necessary to stabilise the power stages.The close you mount them to the grid the better. Marshall never ever made good amplfifiers.Only good for hard rock. If you want a much more cleaner amp, use cathode resistors for example, they even show you if the output valve works properly if you measure across them and give these power valves a longer lifespan

[NZaudio]

Ok here's an amended drawing with PT, OT and choke info.

The input design is taken straight from the original schematic. Each channel has a hi and lo input http://www.pleximods.com/images/66JTM45Schematic.gif

nice drawing, compare yourself

[mort]

'So the stand by should go between the choke and the pair of 470 ohm resistors? (just realized I didn't number those resistors)'
Yes. It doesn't result in a total mute unless a 2 way switch is used to ground the screens - a minuscule signal gets through.

In response to this I've moved the standby, and yeah I do get some bleed through in stand by mode.


And the switch should be wired like this, right?


also an amended total drawing..

[mort]

Of the resistors labelled 1 watt, probably the only one that needs to be is R30.
The V1 cathode resistor is usually 820 ohms, rather than 920.
That implementation of the standby switch is likely to cause excessive stress to the rectifier / premature failure, due to 'hot' switching of a capacitive load; if it's really necessary, better to put it 'after' the reservoir cap or (my preference) on the screen grids.
There's usually a shared 1k resistor in the screen grid supply for JTM45 with KT66.
Pete

Ok I've installed a two way switch to ground the screens. It's wired as shown in the updated drawing. It's still not a total mute. Seems like there's a little MORE signal coming through after installing the grounding switch, while in stand by mode.

Is that shared 1K resistor necessary to make it a total mute?

[big_teee]

What was wrong with the location of the Standby switch in the stock JTM45 Schematic?
In your schematic, you're leaving B+ on the whole amp except the output tube Screens in Standby?
Is that the plan?
T

[mort]

What was wrong with the location of the Standby switch in the stock JTM45 Schematic?
In your schematic, you're leaving B+ on the whole amp except the output tube Screens in Standby?
Is that the plan?
T

Well seeing as I had blown a recto tube (maybe a weak new tube or maybe not), I took pdf64's advice on stand by switch location to be less hard on the rectifier.

Seems you're right though... maybe I implemented it incorrectly ??

[big_teee]

Well seeing as I had blown a recto tube (maybe a weak new tube or maybe not), I took pdf64's advice on stand by switch location to be less hard on the rectifier.

Seems you're right though... maybe I implemented it incorrectly ??

On most marshalls the standby switch is right after the reservoir Cap.
Have you looked at the Metro JTM45 Kit Intructions?
A very nice build manual, with Schematic and pictures.
http://www.metroamp.com/downloads/JTM_45_KIT_V2.1.pdf
Good Luck,
Terry
However on the JTM45 they show it before the 32uf Reservoir.
Don't see why it would hurt to put it right between the 32uf and the choke, before the OT primary.