DB54 - 2254 style compressor {update 22.10.19}

[MoJo]

Hi Everyone,

I replaced all of the transistors that I put in wrong in all 3 boards, and now I can set the BA283 bias calibration to 2.3VDC.

I could not successfully perform the next calibration (step 6 - unity gain calibration). I fed in the 1kHz signal and recorded the output signal. Here are my results:

1) The recorded signal is exactly the same as the input signal when the 'Compress" switch is in the On position; turning any of the knobs does not have any effect on the recorded signal..

2) When the "Compress" switch is in the Off position, I only get a recorded signal if the Gain knob is turned all the way up, but the signal is very low in volume.

3) The meter is not moving at all.

Any ideas on how I can troubleshoot this?

 

[MoJo]

Turning the VR3 Gain Set, as step 6 of the instructions say, have absolutely no effect.

Turning the VR2 Threshold Set, as step 7 of the instructions say, have absolutely no effect.

 

[MoJo]

Studying the schematic for BA191 I saw that I had TR4 installed wrong. I used the schematic to determine the proper orientation, but no change in operation.

 

[MoJo]

I also found that TR5 on BA185 was installed incorrectly, so I put it in properly but still no change.

I was wondering, if I installed transistors incorrectly and applied voltage, does that ruin them?

 

[JMan]

Where did you grab the schematic for the BA185? The one in the technical docs forum looked like it didn't quite match the BOM, and I sort of feel like I missed something. I find it incredibly frustrating when a project like this doesn't come with a schematic of its own, especially when it says right in the project docs that it isn't a 1:1 clone.

 

[Undos]

Hi Everyone,

I replaced all of the transistors that I put in wrong in all 3 boards, and now I can set the BA283 bias calibration to 2.3VDC.

I could not successfully perform the next calibration (step 6 - unity gain calibration). I fed in the 1kHz signal and recorded the output signal. Here are my results:

1) The recorded signal is exactly the same as the input signal when the 'Compress" switch is in the On position; turning any of the knobs does not have any effect on the recorded signal..

2) When the "Compress" switch is in the Off position, I only get a recorded signal if the Gain knob is turned all the way up, but the signal is very low in volume.

3) The meter is not moving at all.

Any ideas on how I can troubleshoot this?

Hi MoJo when the compress switch is off (Up Position on my unit) the gain make up shouldn‘t have an effect. Level should be roughly the same. When you switch in the compression chain (toggle switch in the down position on my unit) the Gain make up should work then. could it be that you are mixing it up (on/off position)? would make more sense ?

 

[MoJo]

Where did you grab the schematic for the BA185? The one in the technical docs forum looked like it didn't quite match the BOM, and I sort of feel like I missed something. I find it incredibly frustrating when a project like this doesn't come with a schematic of its own, especially when it says right in the project docs that it isn't a 1:1 clone.

Hi JMan, sorry for the delay; I took me a while to find it again. Here is the link: http://www.10000cows.com/BA185.JPG

 

[JMan]

Thanks for sharing! That seems pretty close to what the parts list from the project docs lists, with a few component values changed (but nothing major).

I also found that TR5 on BA185 was installed incorrectly, so I put it in properly but still no change.

I was wondering, if I installed transistors incorrectly and applied voltage, does that ruin them?

It is possible that a transistor can be damaged if installed backward, but it's hard to say if that's what happened here.

Hi Everyone,

I replaced all of the transistors that I put in wrong in all 3 boards, and now I can set the BA283 bias calibration to 2.3VDC.

I could not successfully perform the next calibration (step 6 - unity gain calibration). I fed in the 1kHz signal and recorded the output signal. Here are my results:

1) The recorded signal is exactly the same as the input signal when the 'Compress" switch is in the On position; turning any of the knobs does not have any effect on the recorded signal..

2) When the "Compress" switch is in the Off position, I only get a recorded signal if the Gain knob is turned all the way up, but the signal is very low in volume.

3) The meter is not moving at all.

Any ideas on how I can troubleshoot this?

It sounds like there could be a couple problems. Odd that it passes audio when the compressor is engaged but not when in bypass. No effect from turning knobs and no movement on the meter implies no compression, which points to an issue in the sidechain. These two statements, to me, seem like two different problems. I will ponder this a bit over my coffee tomorrow morning.

 

[MoJo]

Hi MoJo when the compress switch is off (Up Position on my unit) the gain make up shouldn‘t have an effect. Level should be roughly the same. When you switch in the compression chain (toggle switch in the down position on my unit) the Gain make up should work then. could it be that you are mixing it up (on/off position)? would make more sense ?

Hi MoJo when the compress switch is off (Up Position on my unit) the gain make up shouldn‘t have an effect. Level should be roughly the same. When you switch in the compression chain (toggle switch in the down position on my unit) the Gain make up should work then. could it be that you are mixing it up (on/off position)? would make more sense ?

Hi Undos,

The switches are ON-ON so I don't think it is possible to put them in upside down. When the Compress switch is in either position, the knobs don't have any effect. The only knob that has any effect (albeit very small) is when the Compress switch is in the Off position (LED is green) is the Gain Mackup knob; and I have to turn that one all the way to max just to get a slight signal from the output XLR.

Also, the Makeup gain trim pot and the Meter trim pot have no effect in either direction. And the meter has no movement no matter what I do.

 

[MoJo]

You all are so helpful and I just wanted to say "Thank you".