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Old 26th February 2012, 05:02 PM   #21
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Yes it looks like there is enough room to also fit the board in horizontally on stand-offs. Ideally you would use a piece of phenolic board the same dimensions underneath the preamp PCB as insulation. Any PC repair place would have millions of those stand-offs for free I would think.
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Old 26th February 2012, 05:10 PM   #22
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It looks like your PSU browned out in exactly the same place as my T-120R. Can you take a close-up of that one section?

Also do you know since these pots have that collar around the shaft up to the panel if they run a ground through that?
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Old 26th February 2012, 06:25 PM   #23
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wow so many posts!!!

Had to dash to eat something lol.

#1: Yes the pots are collared, right up to the back of the front faceplate.
#2: I will try to take a close up pic of various parts, although it depends greatly on how well the macro on my camera phone works

#3: The ground runs thru each leg, and back out again, and in some cases also to points on the PCB. I was thinking along similar lines: to cut legs and just link them, mimicking the original pot casing.

#4: Had written an enquiry email to a guy called Mario, that DM support recommended I contact. Although its been mentioned by yourself (i obviously didnt pay enough attention) He recommended a look at the CD120 schematic on the DM site. Ive done this, and the res is even worse than the t60/t120 scan!!! However i can work out what most components are, and it does seem to be very similar, if not identical to the t120 output stage. From this I now know the 'master' vol is a 10k pot, as is the presence pot. Also the 47k 'mystery mod resistor' I found is explained. It is here on the CD schematic, on the wiper of the bias preset. I can rest assured that this mod isnt going to harm things!

Next I plan to either print the schematics on the A3 printer at work for clarity, and write the component values in so they are readable, OR scan the printout of the scan, and edit in paint, to type the values in for clarity. When ive done this i shall post it.
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Last edited by mondogenerator; 26th February 2012 at 06:30 PM.
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Old 26th February 2012, 07:03 PM   #24
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I discovered that flat black auto lacquer in a spray can from those paint racks at auto parts stores works perfect to touch up the enclosure. It dries in less than five minutes. Beauty of lacquer is you can sand or steel wool it, blends well with existing paint and it is very rugged in service. I used it to paint the handles and enclosure screen cover. It also works well on the transformers, but better in a gloss in black or some other colour.

For screws to hold the enclosure cover I used those stainless steel hex head screws that are normally used to hold down cards in older PCs. They have the right size threads and look nicer than the stock parts.

Last edited by StephaninMelb; 26th February 2012 at 07:06 PM.
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Old 27th February 2012, 03:19 PM   #25
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im not going to touch the finish. too much hassle messing with anodised Alu, and If anything It may go into a case anyhow. Birch ply, yacht varnish.

Sound/electrical restoration is all im concerned with at the moment.

I wonder though....How many of these things were made?
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Old 28th February 2012, 01:56 AM   #26
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Default How many Signature Series T-120 Amps Made

I found out recently from a statement made by "Dean Markley" that less than 200 amps were made of the CD60 type. At the design phase of the CD60 Reissue Dean and Greg Farres were bringing into UltraSound Acoustic Amps (now Dean Markley Amps) any CD60 amps that could be located. They had two and managed to bring in at least one more amp for examination. The CD60 / CD120 had been into sold into the mass market via musical instrument resellers. These amps were never heavily promoted

We know that the T-120 and T-60 had schematics based on the CD60 / CD120 series. And these in turn were based on schematics for the JMF Spectra T-30 / T-60 and T-120 (sometimes incorrectly identified as 7-30, 7-60 and 7-120 models. Dean Markley acquired these JMF designs when the company bought out JMF Electronics.

The T-120 / T-60 amps were primarly sold into the professional market and used to position the Dean Markley brand in that market segment. My guess is that less than 100 units were made of all T-120 / T-60 amp types over all the production years. Certainly an upper range is less than the 200 amps of the CD60 type. This seems to be confirmed by the less than 4-5 T-120 units that are seen offered by sale in any give year across all the eBay International sites. On more rare occasions are seen those amps listed on Craigs List, similar Internet sites or sold via auction (like the two Eric Clapton T-120 amps). Of course there is no practical way to track sales by made by individual musical instrument amp stores, but the number of T-120 amps sold through these channels would have to be extremely small.

I am guessing that somewhere in the order of 50 units of T-60 and T-120 amps survive. On that basis these amps should have a price far higher than what they have been selling for...

Throwing aside that T-120 and CD-Series amps used PCB construction combined with hand-work they were hand assembled amps. Given the small numbers that were built one can truely say that they were boutique amps.

One fundamental mistake made by Dean Markley was that original Signature Series, CD Series and Reissues should have been positioned as boutique amps. They should have also used "hand-made" circuit construction more representative of boutique amp builders, such as eyelet board or turret board (even if the boards were assembled in China).

Dean Markley still has an opportunity to change Dean Markley Amps to a boutique amp business. The best idea might be to buyout Ceratone for their product mix and combine this with Dean Markley sales & marketing. Also to use Dean Markley UltraSound facility as a "custom shop" business organisation. This would give Dean Markley Amps quick access to a large range of amp circuits and kits. To which DM could add 5 to 10 amp circuits outside the vintage Fender and Marshall range representative of the rare amp "Tone Kings." They could then also offered completely built amps with a wide-range of options. They could have one or two assembly facilities in Asia and a custom shop in USA that also does final assembly of any Asian produced sub-assemblies. It would also pay for Dean Markley to look at JoYo in China for mass market guitar tube amp production under a seperate classy "value sub brand." Market tests indicate there would be market acceptance for these products, but they need a better marketing / sales structure.
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Old 28th February 2012, 05:28 AM   #27
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very interesting! Mine has the serial 't120r-047' which would make it one of the final few ever made, if youre supposition is accurate!
Correction, in the middle of the production run. Misread lol
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Last edited by mondogenerator; 28th February 2012 at 05:33 AM.
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Old 20th March 2012, 05:46 AM   #28
sirbevo is offline sirbevo  United States
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I recently acquired a T120 Signature non-reverb head from my father. He found it at an auction in Austin, TX. He called me up, knowing that tube amps are a hobby of mine, and asked me about it before he bid on it. I quickly looked it up but found very little info on it. I said it's probably worth around 350$ and he said he might bid on it. Well.....he did and got it for $70 and quickly sent it to me.

When I got it, the far right power tube was missing and the socket looked like some arcing had happened. I know this can happen when the sockets are worn and the power tube pins are not secure. I bought 4 new sockets and replaced them. I had some extra 6l6WGC Sovteks laying around so I decided to try the amp out. HOLY CRAP! What a beautiful sounding amp this is!!

I've now decided to completely service the amp. I am experiencing a volume drop periodically and pretty sure it's from the electrolytic filter caps.

I cleaned the pots with contact cleaner and they respond well now. No scratchyness.

I purchased replacement Illinois caps from NewOldSounds.com They have the exact replacements for all of them except the 33uf 450v caps. I just went with what they had at the site. Oh, also the 100uf 80v caps are now going to be 100uf 100v caps(Illinois) but measure exactly same dimensions.

I measured the zener diodes(4746-18v) you guys had mentioned for the bias circuit before I replaced them. There was some discoloration on the PCB at where the leads were soldered on these diodes. Fortunately I had some spare 4746's
Original zeners = +17.10 vdc and -17.14vdc
New zeners = +18.30 vdc and -18.00 vdc

I also am going to order some Winged C 6l6GC's and EH 12ax7's. I've used the winged c's in a JCM900 before and was very happy with them.
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Old 11th September 2012, 05:28 AM   #29
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I just joined here and know its and older thread but i too have this amp. Mine is the non-reverb model. I've recently had my gone completely through by my amp tech. BTW serial ends in 185 so gotta be at least 200 or so of these sold. Not sure how many are left though. I'll never sell it, its deffinently one of the best amps for cleans straight up to rock.
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Old 11th November 2013, 08:41 PM   #30
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Links for schematics are dead.
Can anyone help with a current link, or even better, upload a copy of the schematic for the Signature Series 120? I've got one on the bench that has been hacked, original pots have been changed (with used guitar pots!) and I have not found a copy of the preamp circuit to determine correct replacement values.
Any help with be very much appreciated.
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