525 build thread

[emrr]

ah, NFG.  Your avatar is still pretty hot. 

Even Dick is diggin' 'er. 

 

[user 10827]

Hi Peter,

I have all units ready to fit together, some thing does not seem right, the round black caps for the push switches (x6), do not fit though the front panel, and only just through the back plate, is there some thing im supposed to do here? before i go and drill things about..

All the best
Pete

 

[peter purpose]

You must have early panels that need drilling.

 

[user 10827]

cool, no sweat, easy peasy..

thanks!

 

[user 10827]

Hi Peter,

OK, a bit of help needed, units powerd up ok, can hear a little normal hiss as you turn the LESS/MORE knob up so its def on and output stage seems OK.

As soon as you depress IN the test tone drops to -60dB , the INPUT control has no effect, the OUTPUT control does effect this small signal. The VR around A1 does alter the gain of this very small signal too

have i over looked some thing simple, both my units behave the same so i have done some thing not quite to both...any help much appreciated. 

 

[peter purpose]

Have you fixed it?

 

[user 10827]

Hi Peter,

No, i traced the signal into A1, and its coming out of A1 very small, negitve gain out of A1, then i saw a post about C3, which i pulled out, did not help me though, all though if i wind the input right up and the compression full, the lights dance about and makes a sound like a digital phone! lol

but that maybe just done to all the VR's not being set up propely i dont know, as these are new to me.

so some thing is causing the output of A1 to be very small, like the side chain i guess, but im not sure what voltage are supposed to around there..

mmm tricky..

 

[peter purpose]

Have you fixed it yet?

 

[user 10827]

Ha! Lol, thanks, it must be some thing around the fet, pulling the gain of a1 down,

I've given up for now, look tomorrow.
Pete

 

[peter purpose]

Have you fixed it yet?  ;D

I'm the worst troubeshooter on the planet.. isn't I.

Have you gone through any of the set-up procedure?

 

[user 10827]

hey no problem, you are not here just to help me, im good, i need to think what i have done wrong in both cases, i cant think that i have, normally very good as this,

In the set up proc the first thing is to set the level, well i don't have any coming out so failed on the first thing,

it seems to me that the FET is being turned on all the time regardless of the side chain, but i need to look into it further, it has to be a wrong component value or wrong connection with the wiring, as its both units, its unlikely to be component failure.

the MORE/LESS pot is work like a kind of Gain at the moment, its increasing the small signal that i do have, and the hiss increases to, is that normal it should behave like that, as a gain? i guess so, whilst also feeding more signal to the sidechain, is that how it works?

Cheers
Pete

 

[peter purpose]

The more/less pot increases/decreases compression and inc/dec gain accordingly for a constant output.

 

[user 10827]

Thanks peter, as i thought, that's working then...ill look some more.

 

[user 10827]

Hi,

is any one able to measure some voltages for me? so i can compare my unit to yours, I think the problem is around the input amp,

So any DC measurements around the FET, Q5 and A1 would be fantastic.

Best
Pete

 

[peter purpose]

Pete... did you do the cap mod on the input amp?

 

[user 10827]

EDIT : removed some posts for clarity.

Hi Peter,

I think i did correctly, ill check now again, looking at the back of the input amp the top leg of the cap reaches across to the base of Q4?

I have removed the input amp and replaced with a spare 2520 and it works just great!

I can not work out for the life of me whats wrong with the input amp, all components are correct. is there a diagram for the input amp? are there any other mods needs other than the cap mod?

this is the correct list of components to be used?

UPRIGHT OP AMP

Q1 BC184C
Q2 BC184C
Q3 BC560C
Q4 BC550C
Q5 BC560C
D1 1N4148
D2 1N4148
R1 33k
R2 47k
R3 10k
R4 47R
R5 47R
C1 5pF

so now im stuck, some thing some where is not adding up.

Cheers
Pete

 

[user 10827]

But playing with out the input amp fitted it still sounds fab, loads of compression.

so what to do, Peter, do you have a spare working input amp available?

 

[benlindell]

sinestar, been great reading your posts of trying to fix your problems. I've still got 2 of these dead in the water. I tried removing my upright opamp and I got no sound. I did however notice that it had a 100ohm resistor inplace of a 10k so I switched that out and put it back in. I still have no sound when in except for a heartbeat that has now developed that goes away when I switch to limiting.

 

[user 10827]

Hi Ben,

Ah bummer, thats a shame, Check you have + & - on your Op amps,( touch the can of the two big Transistors, one should be + and the other -, if that ok you need to start tracing the audio (use a 1KZ tone then you can use your multi meter set to AC) from the back edge connector into the upright opamp, where it is marked + & - underneath, the level of the signel will be smaller here, thats normal. do you have tone here? if you do check the output of the input amp marked o underneath, do you have signal here?

Best
Pete

 

[user 10827]

Hi Peter,

I've checked the thread but cant find any thing, Is there a circuit drawing for the input amp available?

Cheers
Pete