500 series blue face 1176 rev A - Help thread

[dencul]

These are the instructions I got from The Don.
It works. But remember a resistor on the +wire.

“I normally power it with pin 12 (+16V) and pin 5 (ground)..  and wire a resistor in series on the + pin of the meter LED..  normally around 1k5 to 10k depending on how bright you would like it..  The smaller outer pins on the meter are for the LED.”

I hope it helps

Thank you for the help.  So if I have this right: on + side of meter run a resistor and wire to pin 12, and - (neg) side of meter run a wire to pin 5 (ground)?

 

[MiamiBoy]

Yes, exactly from the outer pins of the meter. But before hard soldering the resistor, try with different values to get the right brightness in the LED, before committing to one

 

[dencul]

It's a thing of beauty. Thanks for the help!

 

[MiamiBoy]

Looks great. Which resistor value did you end up using?

 

[dencul]

I went with the first one I tried, 4k7 (carbon comp, actually read 5k). I figured right in the middle of the range would be the not too bright, not too dim I was looking for. The pic was taken before I thought, "oh, I should pass audio to make sure all still sounds good before a victory lap". Success! Thanks again for your help.

 

[MiamiBoy]

You’re welcome.
I think the brightness is just perfect.

 

[buckethead]

Hey guys,

I need to dig up this old thread. I have a couple of those 1176s and was trying to recalibrate and check them after using them for a couple of years. Lately they started to cut out here and there and sometimes there's some gainreduction happening in bypass mode.

So I started with the q bias calibration, but it seems absolutely impossible - I fed a 1kHz sine at 0dBu (0,775V), the rest is set up as should be. As soon as I turn up the input I get enormous output, more than 10V (>22dBu), so it's kinda impossible to do that setup. What am I missing there?

I really can't wrap my head around did, maybe one of you guys can help me out

Thanks and best regards,
Mathias

 

[robinhuntmusic]

I had to replace the main transistor with the cooling fin. It behaved weirdly at some point

 

[roofRob]

Hey!
New to the board, but long time reader…

I want to add a 1176 to my 500 series chain so bad- particularly the U76a!!!
Given the times- is it currently feasible for a (somewhat) newbie to try and source partial kits for the U76, or rather play it save and just order a FET/500 complete kit @Hairball?

Transformers are „hard“ to get at the moment (Hairball hasn‘t been offering the partial kit for over a year now), I never ordered a preset BOM from Mouser (also some parts seem to not be available), you probably know all of that :-/

All I‘ve built on my DIY journey so far is DIYRE Color Pallettes, OLA5 and Soundskulptor Pres- all complete kits.

Should I just jump on it or wait until shortages/supplychains relax (will they)?

Cheers

 

[roofRob]

Hey!
Following up on my post: I bought all the kits and am still sourcing the rest of the gang...
Can any one of the more experienced builders around here propose alternatives for those two hard- if not not at all- to get parts:

• TDK-Lambda CC6-2412DF-E
  I can't seem to find a dc/dc converter that fits the footprint- the ones I saw are like 15W Traco but do also have one less pin and/or wrong spacings between pins
• Honeywell Pot 5 MOhm 20% 1/2W 308N5MEG
  No clue at all- is it linear? can I use any pot with a decently sized axis?

Any hints are much appreciated- newbie in sourcing myself. BOM doesn't provide alternatives for the above elements...

Cheers!

 

[Bobby Baird]

https://www.mouser.com/ProductDetail/TDK-Lambda/CC6-2412DF-E?qs=F9A14TELRMtUVAYFwYKa0Q==Expected March 2023
https://octopart.com/search?q=CC6-2412DF-E&currency=USD&specs=0Pretty much out of stock everywhere.
https://www.mouser.com/ProductDetail/Honeywell/308N5MEG?qs=VJkZAnU6DY03ykIxXI39Pg==The pot is linear. Just substituent with pot that will fit. same size are smaller. The honeywell is obsolete.
Like this Honeywell 392JA5MEG 5 MEG 1/2W LINEAR 1 Turn Potentiometer | eBay

 

[roofRob]

Thanks Bobby,
that‘s what I saw in terms of the DC/DC.
Am I right I could as well just try wiring up one that might be bigger in terms of footprint and/or Power (that might not fit the PCB)?
https://www.ebay.de/itm/15248986472...3g3g9seQFm&var=&widget_ver=artemis&media=COPY
Or

https://www.mouser.de/ProductDetail/CUI-Inc/PYBJ6-D24-S12-OD?qs=uwxL4vQweFNWSluKqCfTAQ==
As for the Poti I‘ll try my luck, thanks!

 

[Bobby Baird]

You could certainly use a different convertor, and wire it to board. The challenge is going to mounting it securely. Making sure it doesn't inadvertently ground out on anything. Not a whole lot of space for free hanging convertor. You would most likely have to isolate by shrink wrapping, but I'm sure the convertor put off considerable heat. Probably not a good idea. Honestly, I would shelf the project until the part became available unless the designer can assist you with a safe alternative solution to the problem. Wish I could be more helpful.

 

[roofRob]

You‘ve been quiet helpful indeed, since that was an idea I had to shrinkwrap the converter. I wouldn‘t have known which amount of heat to expect but that sounds like plenty.
I‘ll try and reach out to David.
Thanks heaps!

 

[roofRob]

@Bobby Baird the Poti you linked won't be sent to Germany...
It appears 5 MOhm Potis are considered obsolete all over the place, too. The only ones I could find are Alpha Pots and seem to be too big of a body (?).
Also the original one has a 3.18mm shaft, but all I found was 6-6.35mm.
Given something like this with 4.7 MOhm would be the only remaining option to date, what would need to change (resistor values? which? what else?)?
Any help is much appreciated, I want this! :-/

 

[Bobby Baird]

I came across this website today. Series RV6 Mil Spec Carbon or Conductive Plastic Potentiometer
Check out the pec pot RV6 model 5 mil. the bushing is the same a 1/4" the shaft is the same 1/8" and the body is 11.9mm. Whereas the honeywell body is 12.7mm so it will fit!

 

[Bobby Baird]

The Precision RV6 5mil standard configurations is your best option. I use pec pots in lots of my builds.

 

[roofRob]

Hello again and the title of this noob episode:
WHAT am I even measuring?!

I am surely measuring 75% of the components before soldering them.
The moment I got suspicious was when a 4k3 resistor taken from the Mouser bag measured 47k (1%, metal film).
I then started measuring what I had already soldered onto the Main PCB and Control Amp PCB- Fluke Multimeter in ‚Auto‘, but also switching between manual modes.
Most of the components actually are Carbon Composite 5% and as far as I can tell from the color coding appear to be correct values.

Main PCB
ID: Value, Measurement
R14: 22k, 18k
R16: 100k, 51k
R25: 3M3, 2M8
R24: 15M, 2M8
R35: 8k2, 8k9
R13: 47k, 44k
dlyR1: 62k, 42k
R9: 3M9, 1M5
R10: 2M2, 1M5

Control Amp PCB
ID: Value, Measurement
R22: 47k, 44k
R57: 270k, 303k
R42: 182k, 6k6

What did I miss or do I not know (yet)?
Am I measuring anything else apart from the single resistor (probes directly at where the wire leaves the body)?
Is this material of old age (degrading quality)?
Part of what produces the actual magic of the device?
Do I need to buy batches of the parts in question, so that there‘s a chance to find a part in the ballpark of the target value?!

All resistors from Mouser basket. More parts on the boards already but the ones mentioned above are the ones with the largest deviations.

 

[Bobby Baird]

Always measure resistor with DMM before populating with alligator clips to the resistor leads. Don't touch leads with your fingers while measuring because your body can add resistance. Resistance will change in circuit most of the time meaning trying to measure once soldered to board could give you inaccurate reading. One would have to lift a leg of the resistor to get accurate reading in circuit. Not ideal. Just be familiar with color code you should be fine. https://eepower.com/resistor-guide/resistor-standards-and-codes/resistor-color-code/# Carbon Composition 5% at best.

 

[roofRob]

Yeah, I had a diffuse feeling about exactly that.
So I don‘t need to doubt my sanity.
I‘ve been measuring as proposed by you (without any too large of deviations), but then seeing way off values in the circuit, which made me insecure in the end.
I even saw resistance rising gradually to the value whilst measuring (is it there were caps involved?).

In regards to color codes the hardest thing is always guessing the colors

So, thanks for clarifying!