[BUILD] New FET/RACK Official Help Thread - Please read first post!

[Echo North]

Hey Mike,

Just a small discrepancy I noticed in the FET Rack build guide. In the assembly section, the third photo shows the ratio card installed with one orientation (switches solder tabs facing out), then a little later on, it shows it differently (switches solder tabs facing in towards the meter card).

I was having a little issue with getting the ratio buttons to center themselves properly in the panel, then I noticed the latter picture, flipped the card and voila!

Just figured you might want to know, in case anyone else has a little difficulty.

Carlos

One of the images was from an early prototype.  I was to go in a certain way, with the 20:1 ratio on the top. That should be labeled on the PCB.

I believe the 6-pin connector should be facing out towards the main PCB.

I'm too sick to double check one right now.  Look for the 20:1 on the PCB.

Mike

 

[Echo North]

Hope you're feeling better!
I had to turn the older units input up about 2/3 of the way from 24 and the next dot (22 since each dot is 3 units). 
Older unit: 6.63VAC
Newer unit: 9.98VAC

With the inputs matched, I had to turn the output of the older unit up to what would be 17 (1/3 between 18 and the next dot)

Let me know what you think!

Sounds like you're having to tweek the in out by about 1/2 a dot.

That's just tolerance.

Mike

 

[Diamondj421]

Sounds like you're having to tweek the in out by about 1/2 a dot.

That's just tolerance.

Mike

Alright. So I'll just have to tweak a little when running both simultaneously? I can live with that.

 

[csavetman]

One of the images was from an early prototype.  I was to go in a certain way, with the 20:1 ratio on the top. That should be labeled on the PCB.

I believe the 6-pin connector should be facing out towards the main PCB.

I'm too sick to double check one right now.  Look for the 20:1 on the PCB.

Mike

I hadn't noticed the labeling on the PCB. My bad.
Feel better.

Carlos

 

[csavetman]

No water,  alcohol is a volatile liquid.  It'll evaporate in seconds.  Water will just sit on there.

So doing as you described and cleaning the bottom of PCB with 91% isopropyl alcohol and soft toothbrush, leaves a little whitish residue behind after drying. Tried it a few times.
Is this just a cosmetic thing and should I just leave it alone and not worry about this?


thanks
Carlos

 

[clockworkonions]

Hi Mike. So I have and issue with the GR. I accidentally put in C21 backwards. the cap bloated so i disregarded and replaced with a new one.  With a 1k load, i get 0vac at TP22 on all ratios. I get -5.5, - 3.2, -2.3, -1.5DCV at PT21. I've read other posts with similar problems and i've checked, double checked my solder joints and component values. Any help is much appreciated! Thanks

-Chris

 

[Echo North]

So doing as you described and cleaning the bottom of PCB with 91% isopropyl alcohol and soft toothbrush, leaves a little whitish residue behind after drying. Tried it a few times.
Is this just a cosmetic thing and should I just leave it alone and not worry about this?


thanks
Carlos

I wouldn't worry about that. We get that too.

 

[Echo North]

Hi Mike. So I have and issue with the GR. I accidentally put in C21 backwards. the cap bloated so i disregarded and replaced with a new one.  With a 1k load, i get 0vac at TP22 on all ratios. I get -5.5, - 3.2, -2.3, -1.5DCV at PT21. I've read other posts with similar problems and i've checked, double checked my solder joints and component values. Any help is much appreciated! Thanks

-Chris

You're checking with a signal and with GR turned on?

Mike

 

[Diamondj421]

Alright. So I'll just have to tweak a little when running both simultaneously? I can live with that.

The difference between the output knobs when both units are compressing  the same source material is REALLY vast. I have to turn the original unit up to 24 to match the newer unit which is only at 36. Also when I have the active links engaged, the newer unit stops reading. Should I go through and check the active link PCBs? I can't seem to find much info about those.

 

[Echo North]

The difference between the output knobs when both units are compressing  the same source material is REALLY vast. I have to turn the original unit up to 24 to match the newer unit which is only at 36. Also when I have the active links engaged, the newer unit stops reading. Should I go through and check the active link PCBs? I can't seem to find much info about those.

Ya that's not right.  I would start there, with the links.

 

[Diamondj421]

Ya that's not right.  I would start there, with the links.

I went through and checked all of the components. Everything is in its place so I went through and reflowed the solder. Is there any test I can do on this before putting it back in and reassembling the whole compressor?

 

[Echo North]

I went through and checked all of the components. Everything is in its place so I went through and reflowed the solder. Is there any test I can do on this before putting it back in and reassembling the whole compressor?

Swap the active links...see if the issue fallows the links.

 

[Diamondj421]

Swap the active links...see if the issue fallows the links.

Switched the links. No difference. The newer unit sounds muffled though in comparison to the original. Does this give us any direction?

 

[Echo North]

Switched the links. No difference. The newer unit sounds muffled though in comparison to the original. Does this give us any direction?

Not really.  Are you loosing high end on one unit? Is that what you mean by "muffled".

 

[clockworkonions]

You're checking with a signal and with GR turned on?

Mike

Yes sir. So i figured i must have messed something up in my GR circuit. could putting C21 backwards have fried one of the semiconductors? the voltages(DC) for the transistors with attack all the way up and no input are:
            B          C          E
Q7    4.4      14.7    4.7
Q8    14.9  29.6    14.08
Q9    3.4      17.1    2.8
Q10  17.1    29.6  16.9

 

[Diamondj421]

Not really.  Are you loosing high end on one unit? Is that what you mean by "muffled".

Correct.

 

[Echo North]

Yes sir. So i figured i must have messed something up in my GR circuit. could putting C21 backwards have fried one of the semiconductors? the voltages(DC) for the transistors with attack all the way up and no input are:
            B          C          E
Q7    4.4      14.7    4.7
Q8    14.9  29.6    14.08
Q9    3.4      17.1    2.8
Q10  17.1    29.6  16.9

I doubt it. Did you ruin a solder pad when you flipped C21?.

If you have no AC voltage at pad 22 in GR mode you have an issue with your ratio PCB probably.  Look at the schematic...there is a linear path from pad 15, where the AC V is, to pad 22.  Where does it die?

Mike

 

[Echo North]

Correct.

Feed the unit a 200 Hz, 1kHz, and 10 kHz signal with GR off.  Measure them at TP1, TP15, TP17, Output tX Brown and then output between +/-.

They should be roughly the same regardless of frequency.  See if there is a point in the circuit where the HF starts to dip.

Mike

 

[Diamondj421]

Feed the unit a 200 Hz, 1kHz, and 10 kHz signal with GR off.  Measure them at TP1, TP15, TP17, Output tX Brown and then output between +/-.

They should be roughly the same regardless of frequency.  See if there is a point in the circuit where the HF starts to dip.

Mike

Jebus! I've never had such a hard time getting readings before. Even now, I'm getting different measurements but these readings were obtained 2 or more times. The numbers that were still reading differently have 2 values and hopefully one will make more sense to you. I know this isn't super pro on my behalf but I've spend about an hour testing and still can't get a consistent reading. Maybe it's my cheap DMM or maybe it's the unit. Hopefully, you will know!

                          200 Hz                                  1kHz                                              10kHz
TP1                .186VAC                                .186VAC                                          .166VAC
TP15              3.28VAC                                  3.32VAC                                        5.57VAC
TP17              436VAC                                  496VAC                                          .471VAC
Brown          1.905/25.03VAC                .532/14.08VAC                          17.07VAC
Output          24.5VAC                                11.88VAC                                      17.19VAC

Thanks!

 

[Echo North]

Jebus! I've never had such a hard time getting readings before. Even now, I'm getting different measurements but these readings were obtained 2 or more times. The numbers that were still reading differently have 2 values and hopefully one will make more sense to you. I know this isn't super pro on my behalf but I've spend about an hour testing and still can't get a consistent reading. Maybe it's my cheap DMM or maybe it's the unit. Hopefully, you will know!

                          200 Hz                                  1kHz                                              10kHz
TP1                .186VAC                                .186VAC                                          .166VAC
TP15              3.28VAC                                  3.32VAC                                        5.57VAC
TP17              436VAC                                  496VAC                                          .471VAC
Brown          1.905/25.03VAC                .532/14.08VAC                          17.07VAC
Output          24.5VAC                                11.88VAC                                      17.19VAC

Thanks!

Ya that doesn't really help if readings are inconsistent and bobbing around.

If you have a missed up unit it could be anything. Swapped resistor values or cap values can create low pass filters. Bad solder joints can alter feedback networks or how gain stages work.

These are tough ones.  If you don't want to send it in for repair, you'll just have to poke through the gain stages comparing it to your other unit. Again try lower and higher frequencies and see if you can pin point where it differs and look there.

Ya cheep DMM's are pretty worthless above 1kHz.

Mike