Trainwreck Express Sag

[Littlewyan]

Does a Trainwreck Express sag under load? I know the voltage across the 1K choke resistor sags a lot but does the actual HT drop at all?

[martin manning]

I just measured it at about 8V, or 2%, from zero volume to wide open into a dummy load. Just happened to have it out on the bench ;^)

[Littlewyan]

Ha, brilliant! Thanks Martin. I always thought the HT in an Express was quite stiff but I saw a post from Glen saying his HT sags under load. He didn't say how much though.

[Roe]

Very little sag at the anode but some screens sag and presumably some preamp sag. 300mA PT is alot for a small amp like this (6k6 primary). By comparison, marshall used a PT rated for 290mA with a 1.7k OT primary, something which gives a lot of sag

[Littlewyan]

Good comparison. Thanks Roe. Those old Marshalls need sag for the valves to survive!