OR120M, help me date this thing.

Maybe someone can help you date your Orange Amplifier?

Moderator: bclaire

Post Reply
Mattias666
New Member
Posts: 4
Joined: Fri Jun 25, 2010 8:39 pm

OR120M, help me date this thing.

Post by Mattias666 » Fri Jun 25, 2010 9:00 pm

Hey guys, alot of good reading on this forum.
If you would help me date my amp I'd be greatful.
/Matt

Image
Image
Image

Sooner
Orange Master
Posts: 1193
Joined: Thu Apr 25, 2002 6:16 pm
Location: USA-land

Re: OR120M, help me date this thing.

Post by Sooner » Fri Jun 25, 2010 9:12 pm

Looks like 1978: http://web.archive.org/web/200806291318 ... eline.html" onclick="window.open(this.href);return false;
Sooner
AD1512 Serial No. 001

Mattias666
New Member
Posts: 4
Joined: Fri Jun 25, 2010 8:39 pm

Re: OR120M, help me date this thing.

Post by Mattias666 » Fri Jun 25, 2010 9:16 pm

Indeed it does, thanks for that.

a.hun
Duke of Orange
Posts: 9764
Joined: Sat Jun 15, 2002 1:05 am
Location: Amsterdam, Hollandland.nl

Re: OR120M, help me date this thing.

Post by a.hun » Mon Jul 05, 2010 8:36 am

There may well be a date tag inside attached to the board. My OR120M, ser. no. 015637, is stamped 10th Aug. 1978.

If you do remove the chassis to check for a tag DON'T touch anything on the circuit board!!! There may be very high (lethal!!!) voltages stored in the big capacitors long after powering the amp down. Maybe best just to have your tech check this the next time he has the amp open eg for biasing up new power valves. Indeed pretty much certainly a '78 though.


Andy.
aNDyH. :wink:

Ever tried to outstare a mirror?

In the bathtub of history the truth is harder to hold than the soap, and much more difficult to find!

Mattias666
New Member
Posts: 4
Joined: Fri Jun 25, 2010 8:39 pm

Re: OR120M, help me date this thing.

Post by Mattias666 » Thu Jul 08, 2010 1:03 pm

a.hun wrote:There may well be a date tag inside attached to the board. My OR120M, ser. no. 015637, is stamped 10th Aug. 1978.

If you do remove the chassis to check for a tag DON'T touch anything on the circuit board!!! There may be very high (lethal!!!) voltages stored in the big capacitors long after powering the amp down. Maybe best just to have your tech check this the next time he has the amp open eg for biasing up new power valves. Indeed pretty much certainly a '78 though.


Andy.
Interesting, will have a look.
Is the bias fixed on these things or will I have to get it rebiased after replacing tubes?

a.hun
Duke of Orange
Posts: 9764
Joined: Sat Jun 15, 2002 1:05 am
Location: Amsterdam, Hollandland.nl

Re: OR120M, help me date this thing.

Post by a.hun » Thu Jul 15, 2010 7:02 am

Mattias666 wrote: Is the bias fixed on these things or will I have to get it rebiased after replacing tubes?
Both!

'Fixed' biasing is a slightly misleading term. It doesn't mean that it can't be adjusted, only that once it is adjusted it stays at the set level. So yes you do have to have the bias checked for new power valve sets. Make sure you get good strong valves too or the OR120 will trash them in no time. You'll be good with things like JJ or 'Winged C' brand SED Svetlanas. Most other modern ones won't last long at all though as the amp voltages / currents are unusually high.

The other type of amp biasing - 'cathode' biasing - is only found on some lower powered amps (up to about 30W output power). This type of circuitry gives a range of 'self adjust' shifting the bias current both for different valves and for different levels of signal. So while the range can also be adjusted by a tech it doesn't stay fixed at any one level.

Only power valves need bias checks BTW. Preamp valves can just be replaced with no such worries.


Andy.
aNDyH. :wink:

Ever tried to outstare a mirror?

In the bathtub of history the truth is harder to hold than the soap, and much more difficult to find!

Mattias666
New Member
Posts: 4
Joined: Fri Jun 25, 2010 8:39 pm

Re: OR120M, help me date this thing.

Post by Mattias666 » Fri Jul 23, 2010 10:09 pm

Thanks for the info!

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest