FET "Grinder"

[castaeplacpa]

hi
i just finished a fet grinder and i have a silly question: what's the fuse value?
thanks!

 

[gyraf]

Depends on power transformer type and size - and primary voltage. Refer to transformer specs?

Jakob E.

 

[ding]

If its for a power transformer this is what I do. I look at the transformer info and do this math...

VA / primary Voltage * 1.36

...then round up to the nearest mA. So if I got .53481 I will get a 550 - 600. I always get slow-blow.

 

[castaeplacpa]

ho yes thank you, i should have check the transfo more carefully before bothering you here..

 

[gyraf]

I think I used a T315mA when I did my 1176 - it will be something like that..

 

[dipfrik]

…right from my workbench

I definitely found some sweet spots without calibrating the unit right after the first few minutes or in different words: "this board is kick ass"

Any hints for the calibration?

Thanks, Sven

PS: the "DIRT-POT" i a must on the front panel *g

 

[frazzman]

…right from my workbench

I definitely found some sweet spots without calibrating the unit right after the first few minutes or in different words: "this board is kick ass"

Any hints for the calibration?

Thanks, Sven

PS: the "DIRT-POT" i a must on the front panel *g

Complete the good 'ol 1176 calibration steps I'd imagine - q-bias et. al

 

[Gustav]

Great work!

Any hints for the calibration?

I found these 4 easy steps will get you in the ball park, if you aren't too picky about the accuracy of the meter throw. It only takes 2 minutes to do.

1. Adjust the MTR-track trimmer to the center of the dial.
2. Adjust the Q-bias trimmer to zero.
3. Adjust the MTR-Zero, so the meter reads +1dB in GR mode
4. Adjust the Q-bias trimmer, until the meter reads 0dB in GR mode.

And yes - follow the 1176 procedure for actual calibration.

Gustav

 

[dipfrik]

Ok, now the problems are starting

I connected a Sifam VU Meter with no signal (all pots are ccw) and the moment i put the Meter-Switch to show gain reduction the needle cranked up immediately to full scale.
MTR-Track and MTR-Zero has no effect.

hmmm…any idea? Wrong meter? Do i need a special meter?

Thanks, Sven

 

[dipfrik]

Anyone experience the same problems or give me an advice?
The OPTO Grinder is waiting

Thanks, Sven

 

[redcheekmusic]

I have a question about the bypass and meter switches. And I am sure this is could be read from the schematic or something, but I am not wise enough to do so.

So the question is:
Is the toggle switch up or down for bypass, and which of the meter settings are up (and which is down)? I need to know this for the front panel design...

Thanks in advance.

 

[Gustav]

Ok, now the problems are starting

I connected a Sifam VU Meter with no signal (all pots are ccw) and the moment i put the Meter-Switch to show gain reduction the needle cranked up immediately to full scale.
MTR-Track and MTR-Zero has no effect.

hmmm…any idea? Wrong meter? Do i need a special meter?

Thanks, Sven

I wouldn't know where to start trouble shooting going by this sparse info. Compression working? Q-bias calibrated? Just the meter circuit acting weird?

Cranked to full scale, what does that mean?

Standard VU meter should work...

Gustav

 

[Gustav]

I have a question about the bypass and meter switches. And I am sure this is could be read from the schematic or something, but I am not wise enough to do so.

So the question is:
Is the toggle switch up or down for bypass, and which of the meter settings are up (and which is down)? I need to know this for the front panel design...

Thanks in advance.

It depends on which way you turn the board, so its probably easiest to just test your desired set-up in practice.

Gustav

 

[dipfrik]

I wouldn't know where to start trouble shooting going by this sparse info. Compression working? Q-bias calibrated? Just the meter circuit acting weird?

Cranked to full scale, what does that mean?

Standard VU meter should work...

Gustav

Yeah compression is definitely working. And for me it sounds great besides that i need to really fine tune the Q-bias.
I mean the meter needle get hard full swing to the right and stays there.
I use a "SIFAM AUDIO LEVEL METER AL29WF".

What do you mean with "Standard VU meter"

Thanks, Sven

 

[dipfrik]

It depends on which way you turn the board, so its probably easiest to just test your desired set-up in practice.

Gustav

Can you confirm my notes in the picture?

Thanks, Sven

 

[Harpo]

I mean the meter needle get hard full swing to the right and stays there.
I use a "SIFAM AUDIO LEVEL METER AL29WF".
What do you mean with "Standard VU meter"

So with your VU meter in GR mode setting trim the 'zero adjust' trimmer that the needle points to 0 VU with no audio input signal applied.
With input signal applied and the unit compressing, trim the 'tracking' trimmer for showing the same amount of dB gain reduction (needle now moving from 0 VU to the left side of your Sifam AL29 VU meter) as your audio level is compressed/reduced. As both trimmers are a little interacting, you'll have to repeat this procedure some time.

 

[dipfrik]

I mean the meter needle get hard full swing to the right and stays there.
I use a "SIFAM AUDIO LEVEL METER AL29WF".
What do you mean with "Standard VU meter"

So with your VU meter in GR mode setting trim the 'zero adjust' trimmer that the needle points to 0 VU with no audio input signal applied.
With input signal applied and the unit compressing, trim the 'tracking' trimmer for showing the same amount of dB gain reduction (needle now moving from 0 VU to the left side of your Sifam AL29 VU meter) as your audio level is compressed/reduced. As both trimmers are a little interacting, you'll have to repeat this procedure some time.

So that's exactly my problem. If no signal is applied and i switch meter to GR mode, the needle jumps very hard (i mean really hard ) full to the right immediately.
The 'zero adjust' trimmer has no effect at all. I checked the meter on a D-AOC and D-LA2A and its fine. If i switch to output mode the needle goes full left (no signal applied).

I checked also a few other vu meter that i have here and it's on all the same behaviour.

The ratio board is really not that complicated to make big mistakes

Thanks, Sven

 

[Gustav]

I mean the meter needle get hard full swing to the right and stays there.
I use a "SIFAM AUDIO LEVEL METER AL29WF".
What do you mean with "Standard VU meter"

So with your VU meter in GR mode setting trim the 'zero adjust' trimmer that the needle points to 0 VU with no audio input signal applied.
With input signal applied and the unit compressing, trim the 'tracking' trimmer for showing the same amount of dB gain reduction (needle now moving from 0 VU to the left side of your Sifam AL29 VU meter) as your audio level is compressed/reduced. As both trimmers are a little interacting, you'll have to repeat this procedure some time.

So that's exactly my problem. If no signal is applied and i switch meter to GR mode, the needle jumps very hard (i mean really hard ) full to the right immediately.
The 'zero adjust' trimmer has no effect at all. I checked the meter on a D-AOC and D-LA2A and its fine. If i switch to output mode the needle goes full left (no signal applied).

I checked also a few other vu meter that i have here and it's on all the same behaviour.

The ratio board is really not that complicated to make big mistakes

Thanks, Sven

Allright - got it!

When I write things like "Standard VU meter" instead of just "VU meter", its because there are so many variations and parts in he world, and I am excluding all the non-standard-VU-meters, that I haven't heard of yet.

For the problem.

I am not sure this could really be the problem, but please start out by double checking the values of the trimmers you put into the various functions.

Gustav

 

[dipfrik]

Ok, i will check that this evening.

Thanks, Sven

 

[castaeplacpa]

hi everybody.
i have a weird problem, i put myy fetgrinder in a case, wired the whole thing and started to check the psu before connecting it to the main board.
here is my problem: the secondary of the transfomer is only providing +4,75V and + 1,5V. far from the 30V.
the primary wires are the two black ones, and the secondary are a green one, a red one, and a yellow one and a blue one stripped together. and i got these values directly from the wires of the secondaries..
any hints?
thank you!