OverUnity Research

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

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

See http://www.diystompboxes.com/smfforum/index.php?topic=41351.0 (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

.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.

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.....

I go for zeners.

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.

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.

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 (http://www.gmarts.org/index.php?go=217)

(http://www.gmarts.org/pix/schem/a_amp-odis.gif)

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

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

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

Yeah, put it up ION, I'd like to hear that!  :D

.99

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!,,

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

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.

LOL, no need to be embarrassed, it's cool nonetheless. Wait till you hear my clip.   :-[

Did you keep that amp?

.99

Cool stuff, sounds good to me ION

Quote from: ION on 2011.10.26, 00:49:29
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

.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?

.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.

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.

Quote from: Farrah Day on 2011.10.26, 19:47:26
.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

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

Nice build Vince.

I take it the amp still shreds?  :P

.99

Quote from: poynt99 on 2011.10.27, 01:04:50
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?

Rusty gear sounds better ;)

I'll be posting that tune. I need to buy some adapters so I can run my cassette deck into my sound card. I'll be picking those up tomorrow. ;)

Darren

Just an FYI,

The simplest way to use two zeners for this application, is to connect them in series, back-to-back in the fb loop of the op-amp. The two components in question in this circuit are in parallel in the fb loop, and in such a case, they would perform as "normal" diodes only.

.99

I am amazed that the component in question has not been identified, I've looked for stacked diodes, limiter diodes and scanned pictures of older case styles and have not seen anything like it, and yet they obviously went to the trouble of putting them into production.

Here's a thread that talks of germanium diodes in early fuzzboxs:

http://archive.ampage.org/threads/1/fxgd/000105/Germanium_diodes_color_code_-1.html

Ha ha getting closer

Look at this datasheet but it's only got page 150  :'(, Theres a diode with a V Forward of 0.9 and at the bottom it shows the diode package 30 we want. O0

EDIT what we need is the rest of an old diode selection guide, i am now suspecting it's a single diode but with 0.9V forward but is it silicon or germanium.

.99

The only time I ever had seen such a diode was in a power supply from around 1970,
and it was a low voltage Zener.

Most low voltage Zener diodes has a forward voltage of 0,9 to approx. 1 volt.
So if you put two back to back in parallel then you get exactly what you want
in clipping voltage.

GL.

It looks like you may have what was called a low leakage diode. If so, you can duplicate the operation by replacing it with a common small signal NPN transistor using only the base and collector leads.

A 2N3904 should provide about .7V. Add a small resistor in series to bring it up to .9.

I haven't tried that trick in a while. Normally, I would use some 1N34A's.

Quote from: Groundloop on 2011.10.27, 15:14:21
.99

The only time I ever had seen such a diode was in a power supply from around 1970,
and it was a low voltage Zener.

Most low voltage Zener diodes has a forward voltage of 0,9 to approx. 1 volt.
So if you put two back to back in parallel then you get exactly what you want
in clipping voltage.

GL.

This is what I measured today with my meter:

- 1N4148 V_F = 0.58V (as expected)
- 1N34A (Germanium) V_F = 0.24V
- 2.4V, 2.7V, 3.3V Zeners V_F = 0.66V
- 4x 1N34A Ge's in series V_F = 0.93V

.99

Quote from: poynt99 on 2011.10.27, 23:19:43
This is what I measured today with my meter:

- 1N4148 V_F = 0.58V (as expected)
- 1N34A (Germanium) V_F = 0.24V
- 2.4V, 2.7V, 3.3V Zeners V_F = 0.66V
- 4x 1N34A Ge's in series V_F = 0.93V

.99

Different diode types are characterized at different forward currents. What current are you using?

I was using a meter on the "diode" setting, so I assume they were all tested at the same current, which is what we want in order to compare V_F's for application in a clipping circuit.

This is also most likely how that person on the forum made the measurements he posted.

.99

Quote from: poynt99 on 2011.10.28, 00:56:32
I was using a meter on the "diode" setting, so I assume they were all tested at the same current, which is what we want in order to compare V_F's for application in a clipping circuit.

This is also most likely how that person on the forum made the measurements he posted.

.99

True, but when comparing with info on data sheets, you should use the forward test current specified. Temperature also affects forward drop.

So here's that song, Nov, 1984:

A friend (bass player) had some friends (vocalist and guitarist) from the University of Alberta that got together and wrote a song called "Set Fire". My friend and I were jamming with this green jazz drummer at the time, so they all came over to my place and in an afternoon we recorded this song on a 4-track cassette machine for entry into the local rock station's battle of the bands or something to that effect.

My part was to play only the lead guitar. I did one take. My friend the bass player was getting into popping and slapping technique and I suppose he figured this song suited that style.....I didn't think so...judge for yourself. We are off time and the vocalist can not be understood, nor could he sing that well imho. We also had no equipment to speak of (all guitars went direct I think), and the echo was my Boss Analog Delay.

Anyway, it is kinda bad, but we had fun doing it. I'm sure when folks heard this song on the radio they were agreeing with the chorus line of "set fire to me" LOL.

One day shortly thereafter, I was waiting at a place of business to pick something up and suddenly our song came on the radio playing in the reception area....cool  8)

:-[
.99

.99,

Not bad at all!  Better in fact than much of what is
heard today from some of the so-called "stars."

Can you tell us more about the lyrics?  How should
we interpret them?

It would seem that the mystery components have at
last been identified.  Germanium stacks (and silicon
too) were used in biasing complementary output
stages to minimize crossover distortion.  Creative
minds found other interesting uses for them also.

One must wonder how the Fuzz circuit would work with
LEDs in place of the 0.9 Volt Germaniums...


Here's a page (http://www.gmarts.org/index.php?go=217) with circuits and explanations.


.99,
I see the difference in Germanium (soft) and Silicon
(hard) clipping.  Yes, LEDs would clip at a higher amplitude.

Thanks Dumped.

I honestly don't remember exactly what the lyrics mean. Half of the words are unintelligible which makes even more difficult to figure out.

Germanium stacks, yes, but did they come in a single package like that? Later someone figured out how to do the biasing better with a Vbe multiplier, i.e. a transistor.

LED's clip quite hard (and at a higher amplitude) compared to diodes and germaniums, so I like to use them as a "top clip" in combination with a lower threshold and softer clipping diode.

.99

Quote from: poynt99 on 2011.10.28, 03:29:00
Later someone figured out how to do the biasing better with a Vbe multiplier, i.e. a transistor.

.99,

Seriously? Forgive me but I'm more an RF guy and not so much into pn junctions either but wouldn't a V_be multiplier just be a constant current source? And, heavily dependent upon temperature?

I hope the designs graduated from that method. If it was the same as RF there would be problems with thermal delay, age variations, mismatch between relative temp coefficients, etc.

I suppose folks like Peterae are just burning the functions as firmware now  :)

Nice job on the tune. I played it very early this morning and I know it's gonna stick in my head all day, and that's a good thing, that's what record producers want. Could have been on the chart's.

I have only one song that ever received airplay, a spoofy country lament about a farmer whose wife tore down the old outhouse and had installed indoor plumbing "cold porcelain seats and all" while he was out plowin' the high field.

I think it was  played on the"Meatball Fulton" show back in '68, Philadelphia for his "Country Special (comedy) Hour". I never could write anything serious. Fotunately the tape was lost sparing you all any further agony.

On the subject of clipping, wayback I installed a 6AL5 miniature dual rectifier in my Fender Super Reverb for a clipping device. I used variable filament voltage to the tube to control the amount and shape of clipping.

Quote from: WaveWatcher on 2011.10.28, 10:33:05
.99,

Seriously? Forgive me but I'm more an RF guy and not so much into pn junctions either but wouldn't a V_be multiplier just be a constant current source? And, heavily dependent upon temperature?

I hope the designs graduated from that method. If it was the same as RF there would be problems with thermal delay, age variations, mismatch between relative temp coefficients, etc.

I suppose folks like Peterae are just burning the functions as firmware now  :)

Indeed, it is essentially a current source and with the correct values, it supplies a "floating" bias voltage across the driver stage. Attach the transistor body to the output heat sink and set the values correctly, and you have near perfect tracking of the bias voltage/current as the finals heat and cool. So temperature variation/tracking is precisely what you want.

.99

Hi Vince.

Yeah the chorus can be a little catchy I guess.

Too bad you lost the song. I've lost some tapes too that I wish I had back from long ago.

How did your tricked-out Super Reverb sound?

Darren

Quote from: poynt99 on 2011.10.28, 12:31:43
Hi Vince.

Yeah the chorus can be a little catchy I guess.

Too bad you lost the song. I've lost some tapes too that I wish I had back from long ago.

How did your tricked-out Super Reverb sound?

Darren

I think it sounded ok, but lacking some of the sweet harmonics of an external box. I made a number of other mods to that amp that probably destroyed its vintage resale value e.g.

Solid state rectifiers instead of 5U4. I used the leftover 5 volt winding as a power boost / buck (switchable) inserted into the primary.

Beefier power supply filtering.

Added individual bias pots and indicator leds so the bias could be precisely set for each output tube.

Beefed up the light gauge speaker wiring. Eliminated the problematic speaker jack in favor of hard wiring with solder connections to all speakers.

But it was pretty beat up physically when given to me

Added a channel switching relay (mercury wetted contacts) for the overdrive channel.

And all the usual mods. Still have it and it sounds fine. Am using a smaller Hot Rod Deluxe nowadays.

I think you guys have some amazing talents and not just dam good in the electronics field.

It is unfortunate that most never manage to make a living from such talents, specially in the arts area, but when they do, what a life.
I have a friend who was a roadie for Led Zeppelin many years ago now, some of the stories he tells are amazing.

Thing is with anything to do with arts, you don't need to be really good, you just need good publicity and do stuff people like to hear or see.
Look at how much bad music is about and these peole make a living at it.

There's not much hope for me now, i keep forgetting things. it was Led Zeppelin not Thin Lizzy

Quote from: Peterae on 2011.10.28, 15:43:51
I think you guys have some amazing talents and not just dam good in the electronics field.

It is unfortunate that most never manage to make a living from such talents, specially in the arts area, but when they do, what a life.
I have a friend who was a roadie for Thin Lizzy many years ago now, some of the stories he tells are amazing.

Thing is with anything to do with arts, you don't need to be really good, you just need good publicity and do stuff people like to hear or see.
Look at how much bad music is about and these peole make a living at it.

You bet, Peter...  The American rock group "Boston" started at MIT with engineering students, one of whom got his Master's there.

An announcement along those lines:
I've got a job coming up by Christmas working in the engineering field analyzing computer output data starting with, say, naval engineering.   This'll be classified, so that's all I'm going to say about it.

However, I would like to get more into music and electronic music in particular.   It might happen in a few years.

--Lee

I made a very comfortable living in the electronics industry, but music has always been an amateur pursuit and I like it that way. (amateur: one who loves what they do)

Never much of a showman, I was always more interested in the personal side of music, it became sort of a way to journal what I was feeling  with a home studio. Nonetheless, I have been in many small time bands over the years and like to jam with the fellows now and then.

That mixed with a strong interest in the technical side has been an enjoyable life journey. I wouldn't have had it any other way.

http://semiconductormuseum.com/MuseumLibrary/HistoryOfCrystalDiodesVolume1.pdf

Interesting.

.99

Museum?

I thought those were the new models  ;D

Sticking the bias transistor on the heat sink was common in RF too. There were better ways which accounted for the other problems but I think all of that is mute with software based equipment.

Peterae:

I feel really lucky, as I have nearly all of the diodes mentioned in that pdf.

don't have the cat whisker setup anymore tho

Blimey ION sounds like you could open a museum or make a killing on eBay, when i type 'diode 1s' into eBay very little comes up.  8)

Here's a better shot of those diodes.

.99

Darren
Not sure if you have seen my earlier post 29, but that diode package is shown on the datasheet and there are also single package diodes with VF of 0.9V, the only problem is that i could not find the whole data book which identifies which diodes use package 30.

So it is probably silicon and a single diode and probably a 1S series diode, what is needed is the 1993 whole data book and it would be easy to identify which diodes use that package.

http://www.overunityresearch.com/index.php?topic=1162.msg17954#msg17954

Hi Peter, and thanks for helping out here.

V_F specs given in the tables of datasheets are for the maximum value only. This value does not reflect real world applications, and is typically much lower (0.3V for Ge for eg.). The V_F(max) given in most specs sheets for germanium diodes is 1V, so all of those diodes in the datasheet you pulled up could be germaniums.

Using a voltmeter set on the "diode" measurement setting is going to use a relatively small forward current, so the measurement produces V_F's much lower than the max value they publish. V_F(max) is not a very useful spec imho.

Darren

Poynt,

I'm in contact with a retired electronics whiz about this...was wondering if you can supply an image of the bottom (traces, etc) too?

He says he can (likely) tell what (kind) they are simply by how they are connected, and to what.

Robert

No problem Robert.

I am pretty sure they are connected back-to-back in parallel across pins 1 and 2 of the op-amp. In other words, they are in the feedback loop of the op-amp. The other two more familiar-looking diodes are also in parallel in the fb loop, but with a series resistor as well.

So the pair with the series resistor conduct first (assuming the measured 0.58V VF is correct, i.e. a Si pair), but they only limit a little due to the series resistance. This begins the gentle limiting of the over all transfer function. Then a package of 3 or 4 series Ge diodes (two packages in anti-parallel) with a VF of about 0.9 V begin to conduct some time after the first pair, but these conduct fully. "Fully" for Ge diodes means they reach a limiting point, but this point forward is a softer limiting function than Si diodes, and hence the difference in sound and intensity of harmonics produced.

Anyway, here is the bottom side of that pcb, if it helps. I haven't compared it to the other pics I posted, but I'm sure it is the same pcb/circuit.

Thanks,
.99

Quote from: DeepCut on 2011.10.29, 03:26:03
I'd never heard of the cats whisker until i watched th series ION posted, story of electricity, what a marvellous doc for Us The Uninitiated :)

I can't believe the transistor used to be a big thing that looked like a spider that had been in an accident !

DeepCut...
Very accurate, as I see it...

www.don-lindsay-archive.org/talk/transistor.html

Does it look like a transistor or a squished spider?   :o    :D

--Lee