Kenny's Hiwatt pics (tecky stuff only)

[Big_Stu]

Stu... 1970 - mine's both - a switchable model... the plate says DR103 SWITCH; might be a one-off according to Mark Huss - Similar in function to the model used by Dave Gilmour but not in looks outwardly...

Ah, so that's yours! I read about that, a cool function to have & amp to have. I'm surprised there weren't more of them, or none that's turned up yet.
I often muse as to how many of the MIAs on Mark's site are gone (one of Noddy Holder's 201s was scrapped after "blowing up" - that's all I know), or stuck in a barn somewhere or the owners aren't aware of the register.

[Highlander]

I bought mine (with a 4x12 Marshall slope cab and a tobacco SG special with a Bigsby) for £200 from a friend in the 70's - he bought it from someone that told him it was one of 6 built and this one belonged to a guitarist in Savoy Brown - only person I can think of could have been Lonesome Dave as Kim Simmonds was a through-and-through Marshall user - never found any live pics of them from that era so no way of even knowing - I know they were on a list of users back then - no provenance and not that bothered...

Operationally quite simple - instead of the paired normal and brilliant inputs there are just one of each - immediately to the right and between is a seperate jack socket that must be plugged in or she runs at 50w only - a simple wedge foot switch cuts or runs the two outer output valves which are permanantly running but only useable when "switched" on...

[Big_Stu]

Cool, does the switching have any effect on the life of the valves; apart from the obvious that if it's usually in 50w mode the two tubes will work more than the other two?
Do the two that are running but not working have a form of protection? (and I don't mean two gorillas with baseball bats) 

[Highlander]

This is a Gorilla free zone... (cheesy griller) 

Not that I've noticed - the present set of valves (pre and post) I err, borrowed from a brand new Marshall in 1979 (microphonic issues) and have lasted until now... I really should give them back some time...

As for protection/run-off that might be part of the reason MH wanted me to do him a wiring diagrem at some point, heavily overdue...

[clankenstein]

it would be interesting to see if when you turn off 2 tubes it also changes the output transformer impedance.

[Psycho Bass Guy]

Cool, does the switching have any effect on the life of the valves; apart from the obvious that if it's usually in 50w mode the two tubes will work more than the other two?

It's possible to just lift the cathode grounds from corresponding power tubes, which leaves the plates still in the circuit, but the tubes are 'turned-off.' This means there are no issues with impedance. Trace Elliot, who borrowed more than a few Hiwatt production practices and parts suppliers, used this in some of their tube bass and power amps.

[Highlander]

When you switch-in the extra output there is no noticeable noise, clicks or sound other than volume change

it would be interesting to see if when you turn off 2 tubes it also changes the output transformer impedance.

Tony or PBG - which outputs and where to check and I'll let you know...

[Big_Stu]

It's possible to just lift the cathode grounds from corresponding power tubes, which leaves the plates still in the circuit, but the tubes are 'turned-off.' This means there are no issues with impedance. Trace Elliot, who borrowed more than a few Hiwatt production practices and parts suppliers, used this in some of their tube bass and power amps.

Thanks, I won't pretend to understand all of it - or have the need to. I've heard of a couple of guys installing their own "half-power" switch to a Hiwatt but got the impression it was something you had to decide which mode you'd be in before firing it up.

[Highlander]

I presume Gilmour's are the same - click/click/click/click/click - that simple.

I mostly worked in three piece or three + vox so used the boost when the guitarist solo'd and I tended to use chording to fill out the sound.

[Psycho Bass Guy]

When you switch-in the extra output there is no noticeable noise, clicks or sound other than volume change

Cathode lifting would be almost completely silent. There might be slight rise in plate voltage on a meter for the B+ since the overall plate current drops, but since the plates are still loading the OT, it's not like just pulling tubes.

which outputs and where to check and I'll let you know...

The lift would be on the ground to cathode resistor, the "input" of the power tube.

Thanks, I won't pretend to understand all of it - or have the need to. I've heard of a couple of guys installing their own "half-power" switch to a Hiwatt but got the impression it was something you had to decide which mode you'd be in before firing it up.

Just for paranoia, I'd do it in standby, but I've accidentally switched the power (it's a knob on the back next to the DI level knob) on my Trace a few times with no ill effects at all.

[clankenstein]

yes that cathode lifting idea sounds pretty nifty,just make sure you dont lift the grid by accident.

[Psycho Bass Guy]

yes that cathode lifting idea sounds pretty nifty,just make sure you dont lift the grid by accident.

I recommended it to a buddy on Talkbass years ago as a way to tame the volume of his Mesa Bass 400+. Of course the usual "technical corrrection" from the f#cktard wannabe's over there ensued with all sorts of prognostications about output transfromers, the Mayan calandar, and why pubscent bass players kissing ass to company reps are the penultimate in technical experience, but he did it anyway and has been very happy with the results for many years now.

Even in a Hiwatt, you'd have a good five or ten seconds to yank the power before the tube plate went all nova, turned from a nice shade of red to orange and yellow and either melted a hole in the glass envelope or blew the mains fuse. The moral of the story is that if you don't know the difference between a supression grid and the cathode on a power tube's pinout, leave it alone.

[Highlander]

... The lift would be on the ground to cathode resistor, the "input" of the power tube.

Ta Maestro...

[Big_Stu]

Of course the usual "technical corrrection" from the f#cktard wannabe's over there ensued with all sorts of prognostications about output transfromers, the Mayan calandar

  PMSL; seen it so many times - and your description brings one poster (not here AFAIK) instantly to mind.

[Highlander]

I have an admission to make... I er... I bought a skirt today... not for my wife or daughter, but for me... well... for me, sort of... it's a Dress-Stewart tartan skirt... no... not a kilt... a skirt...