Hermida Audio - Zendrive [ goop-alarm ]  [traced]

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Hermida Audio - Zendrive [ goop-alarm ]  [traced]

Postby call1800ksmyazz » 27 Jul 2007, 13:11

Havent heard any of you guys talk about this one so I guess no one has it.

I do have the schematic but a few things are missing like the IC Chip values, transistor values, and diode values, although from the descriptions at the bottom, its pretty easy to tell that the diodes are germanium.

Ok, now its a .pdf file so I cant really upload it, but if someone gives me their email address that can upload it, I will send it to them to upload and post.

By the way, I did try breadboarding it without success. But thats could be from the wrong transistors used, wrong IC chip, wrong diodes, or just something that I didnt do right.

Kerry
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Postby madbean » 27 Jul 2007, 14:39

kma-you might be able to take a screenshot of the pdf and upload that.
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Postby call1800ksmyazz » 27 Jul 2007, 16:22

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Postby madbean » 27 Jul 2007, 16:47

Hmmm.....what could be going on with those trannies? How weird.
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Postby invictus » 27 Jul 2007, 16:56

not really weird... seems like the internal diodes are used as clipping diodes in series with some other "glass" diodes mentioned. 1N64 maybe...
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Postby jt » 27 Jul 2007, 17:03

These must be mosfets in series with germanium diodes.Thanks for sharing.
Last edited by jt on 27 Jul 2007, 17:09, edited 1 time in total.
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Postby markusw » 27 Jul 2007, 17:04

The blue diodes might be Schottky diodes. Should also fit to 0.3V Vf.
Looks interesting! :)
Thanks for sharing!

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Postby kagaxdx » 27 Jul 2007, 17:13

The first opamp is not biased ?? :shock:
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Postby kagaxdx » 27 Jul 2007, 18:01

Should R5 be conected to U1a pin 2 instead of 3?
Even that way U1a is still not biased.

:shock: :shock: :shock: R1 and R2 powers the opamp with ONLY 4.5V?? :?
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Postby Dirk_Hendrik » 27 Jul 2007, 19:13

kagaxdx wrote:Should R5 be conected to U1a pin 2 instead of 3?
Even that way U1a is still not biased.

:shock: :shock: :shock: R1 and R2 powers the opamp with ONLY 4.5V?? :?


Most likely yoy are right. R5 as a biasing diode to the junction of R1 and R2. The "voice' network as part of the feedback loop.

Furtrermore those trasistors connected as diodes .

And supply power through a 10k resistor will not work that well.
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Postby Goop_buster » 27 Jul 2007, 19:43

The schematic is wrong and do not follow the PCB :D
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Postby jt » 27 Jul 2007, 20:32

If we delete the line that connects C2 to Pin 8,then connect positive side of C2 to the right side of R5 and connect Pin 8 to the positive side of C1 it must be OK.Am i right?
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Postby Goop_buster » 27 Jul 2007, 23:16

jt wrote:If we delete the line that connects C2 to Pin 8,then connect positive side of C2 to the right side of R5 and connect Pin 8 to the positive side of C1 it must be OK.Am i right?


I made a quick try to bring order in this mess :wink:

This (see below) is what is going on in the previous PCB at least. However there is some problems. The PCB has no place for a second diode in one of clipping directions. There is also no place for a resistor to the gainpot (as shown first schematic) so that may be placed off board ?? Feel free to make suggestions and/or corrections if there is anything wrong. I used MC1458, 1N34 and 2N7000 based on other hermida circuits.

Image
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Postby goaltoday » 28 Jul 2007, 01:01

Zendrive guts. I suppose the "secret" diodes are under the goop. :P

The schematic now (thanks Goop_buster) looks plausible.
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Postby invictus » 28 Jul 2007, 01:03

this is assuming that the PCB layout is correct..

but what if the PCB is wrong? :? is there a gut shot of PCB solder side somewhere?


..
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Postby Goop_buster » 28 Jul 2007, 01:12

invictus wrote:this is assuming that the PCB layout is correct..

but what if the PCB is wrong? :? is there a gut shot of PCB solder side somewhere?


..


Good point :D I have no idea if that PCB is right. It sure look more plausible than the previous schematic though :wink: :D

Here is another gut shot but same goop there :cry:

http://www.digimart.net/images/64/DS00191845_3.jpg
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Postby call1800ksmyazz » 28 Jul 2007, 02:04

I could always go knock on mr Hermida's door with schematic in hand :lol:

He only lives 20-30 minutes from me. Actually, when I first started building pedals I met him in a local guitar shop (had no freakin idea who he was lmao). My parents were talking to him while I played guitar. If only I knew who he was and knew electronic stuff back then, I would have tried to impress him and try to work for him. Doh! :x
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Postby JHS » 28 Jul 2007, 10:06

The Mosferatu is a AMZ SoS-clone with a few altered values and MOSFETS instead of the diodes. The PCB for the Mosfertau and the part layout is the same on the ZD.

I think the only difference between those two is the clipping section and myabe a few part values.

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Postby modman » 28 Jul 2007, 11:15

JHS wrote:The Mosferatu is a AMZ SoS-clone with a few altered values and MOSFETS instead of the diodes. The PCB for the Mosfertau and the part layout is the same on the ZD.

I think the only difference between those two is the clipping section and myabe a few part values.

JHS


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Postby pf_fan » 31 Jul 2007, 22:36

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