Search found 17 matches

by av500
22 Jun 2017, 10:53
Forum: Boutique Stompboxes dissected...
Topic: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]
Replies: 38
Views: 20210

Re: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]

turns out it was not the EPROM device but the PC, after unfreezing another XP machine with a working parallel port from cold storage it worked...
by av500
21 Jun 2017, 15:13
Forum: Boutique Stompboxes dissected...
Topic: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]
Replies: 38
Views: 20210

Re: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]

darn, the EPROM reader does not work, it always reads the upper and lower 4 bits the same :( and of course it's 20ys old with no support...
by av500
21 Jun 2017, 13:47
Forum: Boutique Stompboxes dissected...
Topic: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]
Replies: 38
Views: 20210

Re: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]

bajaman wrote:says it is corrupt even when renamed
yeah looking at the actual binary data, it looks fishy. guess something went wrong reading it out. back to the drawing board...
by av500
18 Jun 2017, 10:39
Forum: Boutique Stompboxes dissected...
Topic: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]
Replies: 38
Views: 20210

Re: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]

Dirk_Hendrik wrote:Why not?
well, I don't have any idea what the legal implications are. so I err on the side of caution...
by av500
17 Jun 2017, 17:23
Forum: Boutique Stompboxes dissected...
Topic: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]
Replies: 38
Views: 20210

Re: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]

Hey, how is the dumping going? I'm really looking forward to it! I wrote a little disassembler which lets you analyse the contents of the EPROM. I was hoping to fix the broken bytes by the help of that, but it seems there are just too many of them. :( You can find the source code here: https://gith...
by av500
04 May 2017, 12:51
Forum: Boutique Stompboxes dissected...
Topic: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]
Replies: 38
Views: 20210

Re: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]

slowly since coworker decided to give it to a friend so I am waiting for the EPROM reader come back... :(
by av500
17 Apr 2017, 17:14
Forum: Boutique Stompboxes dissected...
Topic: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]
Replies: 38
Views: 20210

Re: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]

I have a working PSA 1 and an eprom reader so I will try to dump it next week
by av500
29 Mar 2017, 09:15
Forum: Boutique Stompboxes dissected...
Topic: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]
Replies: 38
Views: 20210

Re: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]

before you burn another transformer, check the board for a short to GND on any of the three power rails: 1) measure the resistance to GND on the three regulators, 5V, 15V, -15V on both input and output pins, see the internet for the data sheets (7805, 7815, 7915) 2) check the capacitors in the power...
by av500
27 Jul 2015, 11:44
Forum: Boutique Stompboxes dissected...
Topic: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]
Replies: 38
Views: 20210

Re: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]

Further question, av500, on your sketch of the amplifiers circuits you list the unknown IC's (ones with the code ground off) as DS1267. I'm sure that somewhere else on a forum (perhaps this one) I saw that conjecture was that these "unknown" IC might be opamps. Can you expand on how you determined ...
by av500
21 Jul 2015, 10:22
Forum: Boutique Stompboxes dissected...
Topic: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]
Replies: 38
Views: 20210

Re: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]

remove the transformer and then measure the resistance to ground of the +/- 15V supplies. The transformer and regulator overheating means that you most likely have a short circuit to ground. if you indeed find a short, the game is to find what part causes it. remove all caps first, they can go bad e...
by av500
12 Feb 2015, 15:53
Forum: Boutique Stompboxes dissected...
Topic: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]
Replies: 38
Views: 20210

Re: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]

From that to another topic: Those diodes... In back-to-back configuration like that they pretty much have to be Zener type. What's the Zener voltage? Close to supply rails or much lower? It's a somewhat important detail. I just checked, the diodes are marked 1N5230B which makes them 4.7V types: htt...
by av500
11 Feb 2015, 23:13
Forum: Boutique Stompboxes dissected...
Topic: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]
Replies: 38
Views: 20210

Re: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]

From that to another topic: Those diodes... In back-to-back configuration like that they pretty much have to be Zener type. What's the Zener voltage? Close to supply rails or much lower? It's a somewhat important detail. thanks for the insight, I'll have a look at the zeners and report back here. O...
by av500
11 Feb 2015, 23:00
Forum: Boutique Stompboxes dissected...
Topic: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]
Replies: 38
Views: 20210

Re: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]

DimebuGG wrote:Schematic redrawn...
wow, thanks for redrawing this! :applause: :applause: :applause:
by av500
29 Jan 2015, 22:08
Forum: Modern Stompbox Effects (1975 - ...)
Topic: Tech21 - Character Series. [schematic]
Replies: 434
Views: 234951

Re: Tech21 Character Series: anybody cracked one open yet? [schematic]

mxrmxr wrote:
BTW, just got hold of a Sansamp PSA-1 rack preamp. Maybe that can be the next project after this one :wink:
Hi, don't know if you saw, I just posted PSA-1 traces and schematics: http://www.freestompboxes.org/viewtopic.php?f=7&t=25708
by av500
24 Jan 2015, 06:32
Forum: Boutique Stompboxes dissected...
Topic: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]
Replies: 38
Views: 20210

Re: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]

Actually, about the mistic IC, Tech21 uses TLCs (CMOS rail-to-rail opamps, from Texas Instruments) often in their designs. I believe that's the reason to go for +-5V, since those opamps get fried above +-8V (or 16V, whatever you want to name it). Otherwise, I believe that there should not be reason...
by av500
23 Jan 2015, 12:12
Forum: Boutique Stompboxes dissected...
Topic: Tech21 SansAmp PSA-1 PCB traces and schematics [traced]
Replies: 38
Views: 20210

Tech21 SansAmp PSA-1 PCB traces and schematics [traced]

Hi there, this is first post here on this forum, I hope I'm doing this right. Since nobody seems to have done this before and I was sick in bed for a week recently, I used that time to trace the schematics of the SansAmp PSA-1. One "tiny" part is missing and that's the "mystery" circuit inside the b...