i found a gut shot images that should help with that: R9 https://images.reverb.com/image/upload/s--2boxR_oE--/f_auto,t_supersize/v1543681838/quic8ink95kyzvay5syc.jpg R6 https://images.reverb.com/image/upload/s--VCBDi00c--/f_auto,t_supersize/v1543681838/scky7v8tv27yomnfbi2r.jpg copied from a reverb l...

maybe contact Steve Dawson at his new company:
http://root-two.co.uk/about-us/
He designed the vintage modern amps so if anybody knows about the effects loop question he should.

good luck.

I'm just guessing but maybe try the other setting for the loop level. from users guide: 4. Ext FX (-10dBV / +4dBu) This switch offers two different loop levels to enable you to match the type of effect(s) connected to the Series Effects Loop. The higher level (+4dBu: switch ‘in’) suits rack processo...

I'm a little late but the MarshallForum has a workbench tab:

https://www.marshallforum.com/forums/the-workbench.12/

maybe this is what you are looking for but I hope you got your amp in working order by now.

I got my Astoria custom back from Steamboat amps after being repaired.
I'm really liking it!
picture from Steamboats facebook page with explanation of what was wrong:

Hopefully, you get good news soon. I got a call today and the Astoria is fixed! there was a bad connection that was apparently hard to find. I'll pick it up next week after our arctic blast (fortunately with no ice/snow) and after the Christmas holidays. I don't know what connection was bad but I h...

well I just dropped off my Asotria at Steamboat amps to have it looked at. hopefully they will be able to repair the amp instead of saying it's not fixable.

fingers creossed.

Steve; The +/- 15v supply I'm guessing is for the switching, loop and boost. What is the 4700v/100v doing? My amp got knocked the other day and that cap broke (C26). The negative lead broke and the back panel broke/cracked.. Marshall is going to make me a new one after the Holiday, but just wonderi...

well after looking at my broke astoria custom i have gained a few data points for trouble shooting. I was able to get sound when i took the astoria's effects loop output and ran it to a known working amps loop input. but when using a short patch cable between the astoria's send and back to receive j...

well I finally got the amp back yesterday afternoon. took a look at it last night a little. i used my orange amps tube tester to check the tubes. all tested good. except didn't test rectifier tube as tester doesn't test them. I have looked at the top side of the pcb board and I don't see anything ob...

I would get your money back and then offer them some cash for the "unrepairable " amp. If it doesn't work out, you can sell the parts. They would likely just trash it. EDIT: Oops. I saw in the OP that is what you intened to do. Good luck. I think your plan has a chance! I'm still waiting for the re...

Did the Repair Shop state the damage had not taken anything else out in the circuit. Would the Retailer give you another return if you find out the amp needs more work than you want to do. Some components could be wired, as you know depends what component traces are involved. If it were me, I'd giv...

hi all, the Astoria line of amps are turret board construction but there appears to also be some PCB traces on the turret board. I bought an Astoria Custom a few weeks ago from GC's used site and it arrived D.O.A. it powers on but no sound. so GC sent it to a repair shop and they said it was damaged...

I have one set up in my living room.
I last played it a few days ago. :)
I have a second one for the back bed(guitar)room so I don't have to carry one back and forth.....
I never really thought my playing through it sounded like slash.
I just thought it sounded like a good jcm800ish amp.

dj

I like mine. I liked it enough that I bought a second one. One for my guitar room and one for my living room so I wouldn't have to carry it back and forth. A side note, one does sound better that the other. The one that doesn't sound as good (but still sounds pretty good) I had replaced the tubes so...