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[Zen Mod]

take any source ( PC prog or whatever), set 1Khz sine to arbitrary level - say 1Vac as seen on your DVM

set vol to max.

feed that signal to input of pre

measure what you got on output

do the same for both SE and bal inputs

measure both SE and Bal outputs

write what you got here

note - for said test all you need is any signal source and decent DVM; as you're measuring ratio between two (same) signals, no need for ultramegagiga measuring setup

reminder

1Vac in SE In will give 2Vac SE out and 4Vac Bal out

1Vac to Bal in will give 1Vac to SE out and 2Vac to Bal out

if you don't have means to give Bal signal, try feeding pin 2 and pin 3 with your SE signal (no connection to pin1/GND), taking care that source is floating ...... meaning free of safety GND

battery operated PC/laptop is good for that

 

[timkrone]

This is worse than I'd hoped. Obviously I've screwed something up with SE inputs on the left board. Was it like this forever? I can't say, but it's like that now. I ran two tests that produced identical results. I'll do some reading in the thread about SE inputs, but I wanted to post the results. Yeesh.

 

[Zen Mod]

remove JP1+ and JP- shorties

conduct measurement with bal signal in:

JP+ pin1 to GND
JP- pin1 to GND
JP+ pin1 to JP- pin1

all that, to investigate buffers function ( expect same signal in - signal out)

while still powered ON, measure Rdc:

JP+ pin2 to GND
JP- pin2 to GND

all that, to investigate state of xformer windings

edit: in general - be sure that JP shorties are having proper contact; not once people had troubles because fo bad short there; you must feel proper resistance when pushing that thingie on pins
if in doubt - take new shorties, or squeeze contacts on existing ones
if still in doubt, just solder thin piece of wire between JP pins and be done

 

[timkrone]

I made these measurements last night, then did it again this morning to verify. Rdc was a bit of a mystery to me, but resistance seemed like a decent answer. Obviously something wrong with V+ on the left board. Thanks (enormously) for your help.

 

[Zen Mod]

you have procedure for buffer setting explained in Build guide, I believe

re-check do you have suspicious buffer set to proper Iq and DC Offset

in fact - first thing to do - following already conducted procedure, you can check do you actually have signal reaching buffer input

that's "wiper" pad ...... trace it to buffer input , or point me to place where your ref. schematic is posted and I'll tell where exactly to put red probe

write here what you got

 

[timkrone]

.
Whew! Here's the new data. I was getting a bad connection from the wiper pad to the buffer input. Once I got that squared away, things started looking (and sounding) a lot better. Thanks again for the troubleshooting advice.

 

[Zen Mod]

so, it sings now properly?

was it cold solder joint, or bad trace?

 

[timkrone]

It was a bad solder joint, and now it's working as it should.

Thanks again. I learned a lot in the last couple of days.

 

[Zen Mod]

 

[jminassi]

Hi guys,

I am trying to order parts I need for both the Zen Balanced Pre and the Pearl 3. I need the part number for the Schurter PEM for the balanced Zen Pre Modushop chassis. There are some part numbers in Post #3125, but I'm not sure if the SE chassis has the same opening.

Also, can someone explain to me 2 pole versus single pole for fuses? Is this caused by different safety rules in different countries? What should I be doing regarding this in the U.S.?

Thanks,

John

 

[jminassi]

I seem to be in a perpetual state of confusion possibly due to jumping among three different projects......but for the balanced Zen Mod Pre V.4 SMD are we doing snubbers for the transformer? I saw a note from Patrick to leave them out at one point. Then the Zen Modest One redesigned the circuit and they were in. I just ordered the AN-0218 doughnuts. I'm confused and I don't even drink alcohol. I think I'm going blind looking at tiny part numbers.....But I did build the Quasimodo jig and the scope is ready to go. Snubbers or no snubbers, that is the question.

John

 

[6L6]

If the PCB has place for what appears to be 2 sets if snubbers, that’s the board that is ok.

If there’s only a place for one set of components, leave empty.

 

[ItsAllInMyHead]

I'm not sure if the SE chassis has the same opening.

They are the same.

Also, can someone explain to me 2 pole versus single pole for fuses?

A quick internet search or two will reveal more (and be more accurate) than I can type in a minute or two. Here is one result

Snubbers or no snubbers, that is the question.

For V4 SMD, you can install the snubbers, and they'll perform as intended.

I'm confused and I don't even drink alcohol.

Maybe see if a drink clears the mind. (I'm kidding, of course.)

I think I'm going blind looking at tiny part numbers

I understand completely.

 

[ItsAllInMyHead]

On a separate note. My apologies on my astrological predictions... the stars have not perfectly aligned, but Venus is in retrograde and things are looking promising. Kits will (highly likely) be ready for purchase end of next week.

 

[Zen Mod]

which means, Patrick was/is extrabusybee

having available both Aleph Jzm and Iron Pre in Store ....... what's not to like?

Greedy Boy'z dream come true

 

[ItsAllInMyHead]

which means, Patrick was/is extrabusybee

I admit I was too ambitious in my estimated timing for measuring and binning the new batch of JFETs.

having available both Aleph Jzm and Iron Pre in Store ....... what's not to like?


Greedy Boy'z dream come true

🙂 One of my absolute favorite combinations.

 

[jminassi]

If the PCB has place for what appears to be 2 sets if snubbers, that’s the board that is ok.

If there’s only a place for one set of components, leave empty.

Yes, the V. 4 SMD Balanced pcb's each have two snubber locations, Rs, Cs, and Cx, and Rs*, Cs* and Cx*. I assume the asterisk is to differentiate the location of the two.

Thanks Jim.

 

[jminassi]

They are the same.

A quick internet search or two will reveal more (and be more accurate) than I can type in a minute or two. Here is one result


For V4 SMD, you can install the snubbers, and they'll perform as intended.

Maybe see if a drink clears the mind. (I'm kidding, of course.)

I understand completely.

Thanks Patrick. It looks like you could use either a single pole or a double pole switch. In the U.S. double poles are usually used for high voltage devices (240V) as it's a safer way to disconnect from the mains when you bring in two 120V lines to an appliance.

Thanks for all the information.

John

 

[dovla83]

Looks like this pre kit is soon to be available which is great as I just received the chassis from Gianluca!

The question is, will the kit cover everything else or I need to fish around for extra parts? I only have the chassis so far.

 

[jminassi]

You are going to need extra parts. See the description of the kit parts in the diyaudio store. You'll need transformer(s), PEM, front panel switch, volume pots, connectors for inputs/outputs, etc.