View Full Version : Tannoy SR840 Amp…questions
Hi every one
I recently brought myself a BIG nice, non working Tannoy SR 840, it’s in ok condition BUT I’ve come across a mod that I can’t find any info on
There seems to be 2 sockets for tubes, what’s even stranger is the fact it looks factory fitted - it’s dosent look like a amateur job(to my eyes anyway)
- Has anyone ever heard of this ore even better, any first hand experience with this mod?
I’ve previously had great feedback on old Tannoy gear in here, so I’m optimistic, there is someone in here with the experience/ know how
Bonus info: I’m Boeing to send it off to a local radio mechanic shop, whom excels in vintage gear…
Thanks up front for your time
Where are these "tube sockets"?
There are 3-pin XLR sockets on the rear of the amplifier, which parallel the 1/4 inch jack socket inputs. Are you sure you haven't confused the XLRs with 'tube sockets'?
https://i.ibb.co/cyZbmX0/tannoy.jpg (https://imgbb.com/)
If you mean these they are the XLR inputs.
Good amplifier!
Hi
Nope! They are mounted inside the amp and look exactly like tube sockets…
Besides I’m not new to XLR’s…
My main setup is fully balanced, this vintage gear is for my new office
+ I’ve seen tube gear over the years in this hobby
The XLR inputs on the Tannoy amp are not balanced. It is possible that the tube sockets have been fitted so that balancing transformers fitted with 'tube' bases can be used to make the inputs fully balanced.
You would need to trace the wiring to find out.
Lawrence001
24-07-2023, 07:39
I think you'll need to attach photos if you want any opinions, we're shooting in the dark otherwise.
walpurgis
24-07-2023, 07:59
I think you'll need to attach photos if you want any opinions, we're shooting in the dark otherwise.
Definitely.
I have tried uploading a photo, but failed
I’d love to attach photos- but don’t know how to- it seems
https://ibb.co/qrXrChf https://ibb.co/WtDRrR0
https://i.ibb.co/G5B59GL/IMG-2422.jpg (https://ibb.co/qrXrChf) https://i.ibb.co/L5QsTsr/IMG-2402.jpg (https://ibb.co/WtDRrR0)
Jubiii ��
Fist image is the “Tube sockets”
Second image is the whole amp, where they are located in the top right corner
Back to the question/potential problem…I haven’t found any information on this & as mentioned it doesn’t look like an amateur job either
I was going to ask if the sockets were 'octal'. That they are suggests they are for plug in transformers, to convert the XLR inputs to balanced type.
I can't see from the photo if the additional sockets are located close to the inputs. Can you say if the screened cables connecting the 'octal' bases also connect to the XLRs?
If you type Tannoy SR840 into a search engine there are a few hits which show photos and the promotional literature for the amp, as well as reviews.
The additional octal sockets are positioned near the front of the amplifier, so you need to see if they connect to the XLR sockets at the rear.
The sockets are close to the front
Orientation of the picture is:
top(of the pic) = front
bottom = the back of the amp (XLR’s and all)
And unfortunately I have no idea if the cable is screened ore connected straight to the XLR’s, as they are tucked away nicely
This stock photo shows an empty space where the sockets are on yours so looks like it is an after-market addition.
https://i.ibb.co/BKbNTwy/sr840.jpg (https://ibb.co/2YxNc5v)
Not sure it's a good idea to have a valve bang up against that reservoir cap.
I'm not sure if they have anything to do with valves. The SR840 is an amp designed to power the Tannoy monitor speakers. Surprisingly for a professional amplifier the XLR inputs are not balanced, so I believe the octal sockets were to allow transformers to be fitted to make the amp fully balanced.
Jesper's friend will easily find out what they are for, though it is surprising that the transformers are missing.
My thoughts/concern exactly Macca
Not that I’m an expert quite the opposite, and the main reason why I’m in here asking you guys & girls
I was hoping that someone in here might have some knowledge/experience with this “mod”
The amp came from a sound studio here in Denmark, unfortunately the guy who had it is now passed away
I brought it from his son
I'm not sure if they have anything to do with valves. The SR840 is an amp designed to power the Tannoy monitor speakers. Surprisingly for a professional amplifier the XLR inputs are not balanced, so I believe the octal sockets were to allow transformers to be fitted to make the amp fully balanced.
Jesper's friend will easily find out what they are for, though it is surprising that the transformers are missing.
Traffos would make more sense.
Must have been robbed out for some other purpose. I know it does happen that they mod and cannibalise equipment in studios or at least they did years ago,
Thanks guys
I’m sure you’re on the right track…as mentioned, I completely in over my head here, hence my post
Hopefully the repair shop know what it is and what’s missing…
Hi again
I’m “bumping” this post again
- as I’m still hoping that one of you lovely people have had this amp & might know what this actually is
Thanks up front for your time
Kind regards
Jesper
Oh, forgot to mention that I’ll try to keep costs down by buying as many off the “parts” before I send it off to the repair shop
I’m already sourcing out a bunch of new stuff
Hi again
I’m “bumping” this post again
- as I’m still hoping that one of you lovely people have had this amp & might know what this actually is
Thanks up front for your time
Kind regards
Jesper
Image not working for me.
Hi Barry
How? Not showing up or too confusing!?
There was no link to an image.
Can you try again?
Thanks
There was no link to an image.
Can you try again?
Thanks
there wasnt any more pics other than first ones posted on page 2
I know, but sometimes images don't appear on my mobile but do on my laptop and vice versa.
donmarrese
13-08-2023, 11:30
Two solenoids sit in those sockets..for speaker protection.
Sent from my LE2123 using Tapatalk
donmarrese
13-08-2023, 11:30
They are OEM, from factory.
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donmarrese
13-08-2023, 11:35
If you pm your email address to me I can offer you more advice.
Once serviced, they'll have enough punch to control your ATCs. It will be the best amp you'll ever own!
Sent from my LE2123 using Tapatalk
donmarrese
13-08-2023, 11:38
They are OEM, from factory.
Sent from my LE2123 using TapatalkSorry, what I meant to say is those Solenoid sockets are original design and meant to be there.
Sent from my LE2123 using Tapatalk
Hi again guys & girls
I’m back on this, now old thread again, as it’s time to start up old and new projects…
The “tube sockets” I mentioned in my “stating thread”… they are both inside the amp! So not XLR’s & they are definitely some kind of tube sockets (8 ore 9 holes in them, a socket)
The amp came from a now deceased studio technician, so he must have tinkered with it as this addition is by no means standard/original
According to my friend, whom I brought this “beauty” from, he was quite good with electronics/sound gear, witch my friend is definitely not… I’m no expert to say the least, but neither a complet noob, my main experience stems from crossovers and small repairs of amps, turntables, cd machines etc…
One of my key problems is that it seems to be impossible to fine a service manual ore schematics for this amp
Witch in return makes it impossible to return the amp to its former glory
Hope there is one of you knowledgeable people out there whom is able to help me out
Additionally I’ve tried uploading pictures and I’m simply not smart enough to succeed!
I never figured that out- have tried a few times bye now, sadly with the same result every time
Additionally I’ve tried uploading pictures and I’m simply not smart enough to succeed!
I never figured that out- have tried a few times bye now, sadly with the same result every time
try here:
https://imgbb.com/
Copy the 'BBC' code and just paste it into your post.
Firebottle
04-11-2024, 07:56
There is a technical description of the amp here:
https://www.hilberink.nl/codehans/tannoy64.htm
Originaly made by Tresham, this is the only Tresham circuit I can find.
https://www.flickr.com/photos/9106501@N04/2773638739
https://ibb.co/Ws2n1M4https://i.ibb.co/V3qV8zc/IMG-4159.jpg (https://ibb.co/Ws2n1M4)
https://i.ibb.co/rF6yJgL/IMG-4168.jpg (https://ibb.co/0mMJ3kW)
Here is a overview of the whole amp
Including the “tube sockets”, lower left corner
Last but not least:
A picture of how the normal Tannoy amplifier looks inside, for comparison (borrowed from the internet)https://i.ibb.co/QY1snC6/IMG-4167.jpg (https://ibb.co/GCbgktV)
Little side note;
I have, of course, changed the to dead capacitors for a pair of the same value(but higher Voltages rating)
I still can’t find any service manual etc on this amp…
Quite annoying
After a bit more research I found that the 8 pin socket connector inside my vintage Tannoy AMP is:
“McMurdo 8 Pin Octal Valve Socket - Black”
I still have NO clue why and what goes into them, the installation including cables look “factory mounted”/pro/neet
donmarrese
11-12-2024, 22:43
Deja Vue..
A pair of relays fit into those octal sockets. protecting each output channel from sending your speakers to Uranus and back. I'm afraid I don't have a schematic....although I will try and find out what Relays you need...I think they are still available...
donmarrese
11-12-2024, 22:54
Just found this on the net...
https://imgbb.com/S7PSyvQ
donmarrese
12-12-2024, 00:34
The original SR840 had two octal bases fitted on the left hand front of the base, IE when looking down into the amp with the top panel removed , between the front PCB and the amp module .
These two sockets were going to be for the two octal based protection relays, as used in the SR402 etc but when Tannoy insisted on a common amp PCB for all the Tresham amps, the Tannoy engineers had to put the relays on the two PCB's.
Unless this SR840 is a very early prototype where the octal based relays were fitted, all production amps had the protection relays fitted to each driver board. (See previous pic of SR 840)
That's my guess although this may be a 'special' modified by a customer, eg a studio.
Well researched Don.
It took me some time to find the relays on the circuit diagram, but they are there: the symbol for the contacts looks almost identical to that for a fuse.
Sadly we are no nearer helping Jasper with his enquiry. Certainly octal based relays are still available, but we need to know the coil resistance and pin out for those specified by Tannoy.
I've been doing a bit of research myself, and can tell you the octal base relays used for speaker protection in the Tresham power amplifiers have an operating voltage of 12V. These relays are still readily obtainable: I would suggest choosing one with a contact rating of 10A.
The best news is that the pin-out for octal based relays is the same regardless of manufacturer. The activation coil is connected across pins 2 and 7, and the normally closed contacts between pins 1 and 4, and between 5 and 8.
Since two relays are used, one for each channel, it would be reasonable to assume each relay is an SPDT type, but to be certain I would suggest you buy two 12V 10A rated DPDT octal base relays.
Sooo cool!
Thanx guys!!! I knew some one out there knew a thing or two about this old amp
I have since spoken to our local Tannoy-guru, whom use to sell this amp’s, and he thinks I’m nuts for trying to fix this amp �� - So there’s that -
Plus he told me that the amp is supposed to bib 3 times & then turn on…well, it actually did bib 3 times before, when the dead capacitors were in it, now however it only bibs once…with brand new Cap’s in
Non of the fuses ar shot, so the mystery continues
But I’m still determined to give it my best shot - so I’ll try to find this parts, any help in that regard(like a link ore a shop) would be greatly appreciated
Thanx - a little to small for me to read, even when I zoom in
https://i.ibb.co/J5m7PTj/IMG-0162.png (https://ibb.co/Gcn2jDQ)
donmarrese
21-12-2024, 22:26
Well done Barry for that research...was waiting on a reply from my Tresham God.....
donmarrese
21-12-2024, 22:35
[QUOTE=Nordlys;1383786]Sooo cool!
Thanx guys!!! I knew some one out there knew a thing or two about this old amp
"I have since spoken to our local Tannoy-guru, whom use to sell this amp’s, and he thinks I’m nuts for trying to fix this amp ��"
Don't listen to him!!! unless the transformer is shot, (and you can obviously test each rail) this beautiful amp can be ressurected from the dead....
"Plus he told me that the amp is supposed to bib 3 times & then turn on…"
That is correct, time lapse of about 5 seconds...Green light flashes..... it stops current surge to the driver boards. Unless you put the relays in those Octal sockets, less than nothing will come out of the amp....and whenever testing, turn the gain controls right down, (which are situated behind the "Tannoy" blanking plate on the front panel of the amp.....)
donmarrese
21-12-2024, 22:36
Thanx - a little to small for me to read, even when I zoom in
Email the guy to get you a full blown copy? I gave you the link.....
donmarrese
21-12-2024, 22:37
https://i.ibb.co/J5m7PTj/IMG-0162.png (https://ibb.co/Gcn2jDQ)
Yes, they look like the ones you need!
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