Grampian RA 7

[chris king]

Has anyone got a Grampian manual and schematics for the RA 7 amps and power supply. I have one but there must be two as the tubes on my amp are different to my schematic. The tubes in mine are correct, their numbers are printed on the chasis. one amp uses kt 66 tubes the other uses 811a any help would be most grateful. my amp uses the 811a tubes my scematic is for the kt 66 tubes

thanks people.

[markrob]

Hi,

I think this is what you need:

[Stevie342000]

If you compare the two circuits the Grampian RA7 using 811A output tubes is similar to the Gotham PFB150 and the KT66 version will be similar IMHO to the Presto 92A (is it) that uses 4 x 807 output tubes (I have never seen the Grampian KT66 version of the schematic) but the BBC modified the Presto 807 amp to use with the BBC cutter head, so it makes sense to me. The RA7 predates the PFB look at the dates on the schematic and as far as I can remember it was imported into the USA along with BBC feedback cutter head by Reeves/Soundcraft. It is very hard to find any schematics on line for the Grampian cutting head power amplifiers. Never seen a manual but there must have been manuals, I have only ever seen this schematic.

[chris king]

thank you could you please email me this direct to my email address? do you have a complete manual of this version ???. ill get you a copy of the one I have, so you have them both. my direct email is classiclambretta@btconnect.com thank you kingy

[chris king]

ill send you a full scan of the manual

[chris king]

do you have a scematic for the power supply???

[Stevie342000]

Hello Chris

PM Sent

I do not have a full manual the schematic tells you all you need to know, as it states AC voltages at test points on the valves and pretty sure it states in feedback links or the bottom of the schematic how to set bias points, it has been a while since I looked at it.