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Author Topic: Component Identification  (Read 71091 times)

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It's not as complicated as it may seem...
Wondering if I can get some help with these components?

I believe they are diodes, but not certain. The diodes to the left are probably typical signal, and they were apparently measured to have a 0.59V Vforward. The black and white components may be diodes, and they were apparently measured to have a Vforward of about 0.9V.

I was thinking they might be varactor diodes. Any ideas guys? If it helps, this is a Japanese made overdrive pedal from the 70's and 80's. (see inside the black circle)

Thanks,
.99
   
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I think they may be round rectifier diodes, but they are unique looking.

See http://www.diystompboxes.com/smfforum/index.php?topic=41351.0  at the bottom of the page, similar looking item.

I might need one of those transistors, trying to duplicate my old Korg MS-10's white noise generator. :) (2SC-644R and 2SC-1685S)

Robert
   
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.99

The 6552 is a dual op -amp from NJM.
NJM6552 is a copy of the AN6552.
NJM4558 is a copy of the AN4558.

The two diodes is most probably Zener diodes used to clip the audio signal.

Unsolder one of the diodes and test the diode by increasing Vin until you get a stable Vout.

If you always get only 0,6 (approx.) volt Vout by varying the Vin from 1 to 12 volt, then the
diode is NOT a Zener. If the Vout reach a fixed level of voltage regardless of Vin,
then the diode is a Zener and you also have found the Zener voltage.

GL.
« Last Edit: 2011-10-25, 08:05:38 by Groundloop »
   
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Hi,
Can you take another photo of the underside of the board and the number from the chip. Its to see how these components are wired in the unit.
I had an Ms10 a long time ago and made a frequency divider board fed from the vco to a socket on the side which patced into the input on the front. sounded like the MS20, good old days.....
   
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I go for zeners.
   

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It's not as complicated as it may seem...
Thanks guys.

GL, these "diodes" are directly in the feedback loop of the op-amp, so if they were zeners, the forward diode inherent to them would conduct on the other half cycle rather than them being reversed biased. I think they are used as the final clip point indeed, but I doubt they are zeners, and I doubt they are rectifier diodes because of the very small lead diameter. Thanks for confirming the op-amp. I thought it was a 4558, and I'll either use a modern variety of it, or something with lower noise.

Here are a couple more pictures. These are not my pictures, as I did not take them. I found them on another forum. The schematic was drawn by someone on that forum, and he is showing the unknown components as capacitors in the fb loop.

I am trying to find the schematic for a "Volz Overdrive" pedal that I used to have many years ago. It sounded great, but I sold it. Now I would like to either buy another or build one. They are hard to come buy.

It seems this small Japanese company back in the 70's and 80's manufactured a line of pedals but put several different brand names on them and gave them slightly different packaging at times as well. A few of the names were:

Electra, Boston, Redson, Volz, LocoBox, etc...

Regards,
.99

PS. the yellow "M1" and M2" are for "Mystery" components.
   
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I'm gonna guess they are germanium diode stacks, probably 3 pellets per unit to get the forward voltage of 0.9 volts.

These were used extensively as bias diodes in early transistor amps, and small transistor radios for thermal compensation of the output stage or other biasing needs.

In a stomp box distortion pedal, the stacked germanium pellets would give a nice soft knee to the forward conduction curve  and give something close to a tube sound.

I played with a lot of this stuff in the late 60's when I was rolling my own guitar amps and distortion boxes, but don't ask me now, I've forgotten most of it.


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"Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy
   

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Buy me some coffee
I am going to guess they are also stacks probably 2 diodes in series.

EDIT They suggest using the TL072
http://www.gmarts.org/index.php?go=217

   

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It's not as complicated as it may seem...
Peter/ION,

Yes, although I've never heard of series-stacked diodes in a package, I would tend to agree that 3 germaniums makes perfect sense.

I've played with various diodes (and combinations thereof) a number of years back when I was designing these types of pedals and more sophisticated preamps, and indeed the germaniums are quite stretchy, and never really give you a hard flat top clipping like silicone diodes do. 3 in series would give about 0.9V as ION mentioned.

Rock on dudes and dudettes!

.99
   

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It's not as complicated as it may seem...
Perhaps when I have time, I'll put up a song that was recorded with some friends back in 1984 with me using this Volz Overdrive pedal for the lead parts. The song is fairly bad, but the guitar tone is alright.

btw, this is what the pedal looked like:

.99
   
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POYNT

Now if you are gonna put up a song, I might be forced to put up one of my band back in 1967.

 It used my very first heavy handed approach to fuzz, a selenium rectifier and power rheostat series connected directly across the power amp  output.

Crude, but what a sound!!! LOL


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It's not as complicated as it may seem...
Yeah, put it up ION, I'd like to hear that!  :D

.99
   
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OK promise not to laugh too loud, recorded on a cheap recorder, and the song was one of those  drive in movie motorcycle gang type, I had seen the night before, maybe from"THE TRIP". Nothing fancy here folks.

We thought we'd give it a shot and it was our first and last take. We were young then, but should have known better. ;)

Actually it was 1966.


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It's not as complicated as it may seem...
Wow!,,

Groovy sound and song there Vince.

ahhh...tape dropouts ;) recorded in a garage?

That's incredible the sound you got from simply clamping the amps output. What amp were you using?

 O0

.99
   
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Thanks POYNT, but that stuff was really crude.

 Recorded in an unfinished basement.

 Amp was a homebrew p-p 6L6's, Dynaco circuit with a little extra preamp gain. Speakers were misc. salvage from old TV's. We were poor.

  Don't ask any more questions, I'm too embarrassed.


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It's not as complicated as it may seem...
LOL, no need to be embarrassed, it's cool nonetheless. Wait till you hear my clip.   :-[

Did you keep that amp?

.99
   

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Buy me some coffee
Cool stuff, sounds good to me ION
   
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OK promise not to laugh too loud, recorded on a cheap recorder, and the song was one of those  drive in movie motorcycle gang type, I had seen the night before, maybe from"THE TRIP". Nothing fancy here folks.

We thought we'd give it a shot and it was our first and last take. We were young then, but should have known better. ;)

Actually it was 1966.
Wow, that's not bad at all!   You were better than a lot of San Francisco street musicians I hear daily.   I have a musically-inclined relative(brother) and I've listened to a lot of chords.

Remember, the actor/musician Jack Black started out in a garage band and look where he is now.

On topic, Pointy,
I'd vote definitely for diodes, but since they're so old and foreign as well, I'm not sure whether they're Zeners or not.   I can read foreign schematics pretty well, but I hardly ever see foreign PC boards that old and foreign, to boot.

--Lee
   
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.99, I have zener diodes that shape, but grey and you seem to have ruled out zeners now. However I've also seen tantalum bead capacitors of similar shape - would they make any sense in that position?
   
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.99

I have looked at several pedals form that time area and they all did use
1N914 or 1N4148 or close clones to these diodes.

Regards,
GL.
   
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Here's a picture of the old amp and speaker cropped out of a much bigger photo, so resolution is not so good.

The very large transformer in the middle is a Dynaco A440, way oversized for the amp but later replaced with a transformer commensurate with the output of the amp's 6L6's.

 I got the output transformer at a surplus store (Fertik's) for one dollar, and was the only output xformer I had at the time. But what a steal at a buck!

Below is the homebrew speaker on castors.


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It's not as complicated as it may seem...
.99, I have zener diodes that shape, but grey and you seem to have ruled out zeners now. However I've also seen tantalum bead capacitors of similar shape - would they make any sense in that position?

Hi Farrah,

Yes, pretty sure they are not zeners. You require another diode in series with a zener in order to block the forward bias state of the zener; and the schematic doesn't show anything in series with those two components.

Tantalum capacitors typically don't go lower than a value of 0.47uF or so, and putting two of those caps in the fb loop would kill all the gain completely. I can assure you they are not tantalums either. ;)

I am pretty convinced they are in fact germanium diodes, perhaps stacked as ION and Peter suggest. I remember sweeping them and they do stretch quite a bit, never really clipping that hard, and hence the smoother sound when using them.

Regards,
Darren
   

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It's not as complicated as it may seem...
Thanks GL,

Indeed, the 1N4148 is what I used mostly in my designs. Later I'll post part of a design I developed back in about 1992. I was getting creative with combining zeners, diodes, germaniums etc., not to mention all the FET switching to change configurations and tone shaping.

Thanks for posting the schematic of the original Tube Screamer.

.99
   

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It's not as complicated as it may seem...
Nice build Vince.

I take it the amp still shreds?  :P

.99
   
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Nice build Vince.

I take it the amp still shreds?  :P

.99

I think it is shredding (rusty) metal in the basement.

Will you be posting that tune?


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