New Very Old Amp Day!

Aidanspaghetti

This thing is just begging for a slide and a trem pedal..............

RiftAmps

ICBM said:

As far as I know all direct-rectified equipment does. It should be a fairly simple job to rewire them for parallel when fitting the mains transformer though - assuming they're all 6.3V types.

Those KT33C have 26v heaters @ 300mA, I've got one (Marconi) spare that I pulled from a radio and haven't had anything to put it into, let me know if you need it.

ICBM

Ah, I didn't know that - I assumed they were like other KT series valves. That makes things a bit more complicated.

The best thing might be to rebuild it for standard 6.3V types like 6V6s. If you do want to keep the original valves, it may be easiest to use a simple 240V-240V isolation transformer - it would be horribly inefficient to use the resistive voltage dropper but it probably doesn't matter that much!

ecc83

"As far as I know all direct-rectified equipment does. It should be a fairly simple job to rewire them for parallel when fitting the mains transformer though - assuming they're all 6.3V types. "

As you have now discovered IC, AC/DC kit has a variety of heater VOLTAGES but the same current.

Rather than go to the great trouble and expense of rewiring the amp I would just get it working with  a standard 1:1 workshop mains isolation traff then fit a smaller (50VAish?) isolator and earth the chassis. This then keeps the amp working almost as it would have done when dangerous! One thing alone will probably affect the sound and that is the half wave rectification. Technically very bad now of course but going to be very "saggy" I bet!

The only reservation I have is whether equipment so modified is still legal? If it passes a PAT test I cannot see why not but then I am not a technical lawyer!......I would certainly not sell the thing!

Dave.

ICBM

ecc83 said:

As you have now discovered IC, AC/DC kit has a variety of heater VOLTAGES but the same current.

Yes, that makes sense. Obvious when I thought about it! Doh .

ecc83 said:

The only reservation I have is whether equipment so modified is still legal? If it passes a PAT test I cannot see why not but then I am not a technical lawyer!......I would certainly not sell the thing!

Nor me. I recently refused a job on an old DIY-built amp for exactly this reason - not because it wasn't safe or couldn't be made so, just that I felt it was unwise to personally guarantee it. The owner wanted it fixed up to sell it - I suggested he simply sold it as-is and let the buyer worry about it. It probably ended up about the same in money terms - to him anyway, not to me, but I can live without the risk.

Aidanspaghetti

Well she's in with the amp surgeon for a make over... He's going to check her yet and impossible resurrect her and if possible make one of the inputs a line in. Should be fun to mess around with. Fingers x'd she's rescuable! I'll update the thread when I have her back and if it's serviceable will do a video...... Cheers!

Nerine

Can people please learn how to use the HTML link in photobucket to embed the pictures into the thread.

It's no extra work than pasting the link from the address bar.

Aidanspaghetti

? All pictures show up here.... On iPad anyway....

boogieman

Photobucket links are awful if you're browsing on iPhone. I usually refuse to click on them as it usually takes an age to load, then diverts to umpteen pop ups (and worse). I got tempted this time though, but all the links above come up as the same pic of a Hiwatt head.

57Deluxe

Aidanspaghetti

Thanks for that! Was that Carlos Rios on that record?

Aidanspaghetti

Update! 
Looking for a U31  and some 6BR7 (ef86 swappable?)????
Can anybody help a (paying) brother out??

ESchap

I might have a spare 6BR7, I'll have a look tonight.  there are currently GEC and Marconi U31's on Ebay for £20 approx.

Gadget

Anthony Matthews at Tube Distinctions might be able to help... www.tubedistinctions.co.uk

ESchap

I don't have a spare 6BR7, I'm afraid.

Aidanspaghetti

Ah thanks a lot for looking!

therose789

Very Nice! 

Good luck with the restoration! 

ESchap

Aidanspaghetti said:

Ah thanks a lot for looking!

There are a couple of Brimar's on eBay just now, but they are auctions.  Langrex are showing 608 (!) in stock.   He's not the cheapest, but very good and his NOS really are NOS ie unused!  You need to call or email for a price.

http://www.langrex.co.uk/stocklist.html

russh

I hope it smells suitably vintage too!
  

Aidanspaghetti

Well shes up and running! A couple of teething problems getting spare valves etc but shes finally working and sounds fantastic
Ive just come away from a session with the TV15 and my Matchless Chieftain in a stereo spread with a few delay and mod pedals....  What an amazing sound - love the 2 amp thing
Ill try and record a video for s+g's