Old beast after tidy up (1969 ORST)

Maybe someone can help you date your Orange Amplifier?

Moderator: bclaire

Post Reply
LD50
Tiny Terror
Posts: 112
Joined: Thu May 19, 2016 8:35 pm

Old beast after tidy up (1969 ORST)

Post by LD50 » Thu Sep 05, 2019 8:28 pm

Further to the post by Silverfox I have an update.

viewtopic.php?f=4&t=27194&start=15

The amp is now up and running. Just need to soak it fully before putting two of my last NOS Mullard xf2s. It is a bit louder and cleaner than my clone as it runs a plate voltage of 525v on the outputs (vs 490 on my clone).
Image
Image
Image
Image
Image
Image
After:
Image
Image

bclaire
Forum Moderator
Posts: 17905
Joined: Thu May 02, 2002 9:19 pm
Location: Outside Boston MA, USA
Contact:

Re: Old beast after tidy up (1969 ORST)

Post by bclaire » Thu Sep 05, 2019 11:43 pm

Wow... very cool. Shoot a video once it's up and running!

Any idea what it says on the back....?

LD50
Tiny Terror
Posts: 112
Joined: Thu May 19, 2016 8:35 pm

Re: Old beast after tidy up (1969 ORST)

Post by LD50 » Fri Sep 06, 2019 7:22 pm

Thanks
So far I am having oscillation issues when volume is above 2nd notch, up to that point it is, as is usual for these pretty loud and has nice touch dynamics, it is quite a brighter than usual and very loud (with the 1M chassis pot turned up to max - the sound is fatter and more full that way). It is a bit spiky with a strat but plenty of beef with my LPR0.Problems come with volume over 2.
I have cleaned and D100 treated the switching jacks and rechecked the bias (shunt voltage on the primaries are not particularly stable yet the grids are solid at -50v).
I have measured the cathode bypass caps in the preamp and first two are 200-300uF but PI one is 0uF, albeit in circuit and they should be 47uF. I have some more of the correct value on the way and will probably replace the bias caps before I risk my NOS Mullards.

Other point I note is the dropping resistors after the screens are 200R x2 in series (not stock). I replaced one with a 10k - what I have normally seen here but left the other at 200R (I've seen a couple that just have a link where the second resistor is.

Anyone else have an early one of these? I've worked on 3 now - all slightly different!

LD50
Tiny Terror
Posts: 112
Joined: Thu May 19, 2016 8:35 pm

Re: Old beast after tidy up (1969 ORST)

Post by LD50 » Sun Sep 08, 2019 8:40 pm

Update
The issue was the ground wire from the drive pot was not making good contact with the ground lug on V2.
With that sorted everything came good.
It is, of course I am biased, fantastic. Very loud, very dynamic, at moderate volumes with boost down a warm clean Orange tone and with the volume and boost cranked very dirty too.
I am grateful to Silverfox for his assistance in selling it to me.
It needed a good clean and a scrub.
I superglued the floating paint down to the chassis
Replaced both octal sockets
Replaced the bias caps
Remade the rectifier (I used UF504, 3A ultrafast recovery diodes
Replacement front panel
New pilot lamp
NOS RS 100uF 450v filter caps (with added 220k bleeders).
I'll make some quick clips soon.

Orphin
Duke of Orange
Posts: 6626
Joined: Wed Sep 15, 2004 9:04 pm
Location: Sweden

Re: Old beast after tidy up (1969 ORST)

Post by Orphin » Tue Dec 22, 2020 6:40 pm

As an ORST owner myself I started saving all the pictures I can find of other ones than mine.
I see that I already have pictures of #028. One of them is quite odd. It was taken with the faceplate off and underneath it's written with a felt pen "Bullsh!t" (with an i) with two arrows pointing at the Depth and Drive controls. Then it's written "More bullsh!t" to the left with an arrow pointing to the Volume control.
The knobs are attatched to the pots so I assumed that this amp didn't have a faceplate. I'm glad it does. :)
David
I'm speaking out of my a$$. Yours might differ.

LD50
Tiny Terror
Posts: 112
Joined: Thu May 19, 2016 8:35 pm

Re: Old beast after tidy up (1969 ORST)

Post by LD50 » Sat Jan 30, 2021 5:49 pm

Sorry to be so slow
Not been here for a while as the vintage orange discussion has been a bit slow and as you will see I was seemingly posting to myself on some threads.

This is the same amp. I bought it from the gentleman that posted the pics originally. I restored it to full working order and it is loud and proud (not as much as my OR120s or GT120!).

I had a bundle of Ormat panels that I had made for restoration purposes, some ORST (without stage/studio on the drive pot) and some OR100 (with the stage/studio legends). In fact I have a couple of spare 100w ones if any one is in need. High quality Trafolyte completely indistinguishable from the originals. Feel free to pm me. I also have a couple of spare chassis with panels, lamps, front handles ready to have transformers etc fitted. Not a commercial exercise, just spares left over.

Post Reply

Who is online

Users browsing this forum: No registered users and 24 guests