91

EQ573 Equaliser / Re: Signal going through the unit but it doesn’t effect the sound

« Last post by JPK on October 31, 2025, 03:09:12 PM »

It looks like it stays in bypassed mode. Check the solders on the relays, R12, the switch SW2 and check the direction of the diodes D1 and D2.

How can I go about supplying power to it outside of the rack
You will need an XT500.

92

First Aid / Re: lunchbox help noise and buzz.

« Last post by JPK on October 31, 2025, 03:03:28 PM »

This modification was for the CP5176 compressor. It has now been integrated into it for a long time.

93

First Aid / Re: lunchbox help noise and buzz.

« Last post by Consigliere on October 31, 2025, 01:50:43 AM »

thank you for your input JPK.

Searching the net I found a link to a document hosted by soundskulptor but it doesn't exist anymore... Is it still available and something to look in to?
http://www.soundskulptor.com/docs/cp5176-bento6-mod.pdf

thanks.

94

EQ573 Equaliser / Signal going through the unit but it doesn’t effect the sound

« Last post by Colindsv on October 30, 2025, 03:25:29 PM »

Just finished building.  

When I send signal through the EQ and twist the knobs.  Nothing is happening. 

There’s nothing shorted to the chassis plate.  No smoking or burning smell.  On visual inspection everything looks normal. 

I’d like to be able to run through some of the voltage tests, but I can’t connect to the test points with my DMM since it needs to be in the rack. 

How can I go about supplying power to it outside of the rack so I can test DC voltages at the various points noted in the troubleshooting guide above?

95

First Aid / Re: lunchbox help noise and buzz.

« Last post by JPK on October 30, 2025, 09:56:33 AM »

Bento power supplies are known to be very noisy, at least for the early models.

I've never heard these noises before but I only had eq's and compressors in it before.
That is because a pre has more gain.

Is it a grounding issue?
Probably not.

Transformer issue?
They are switching mode so you won't be able to change the transformer.

Is it worth mod'ing or repairing?
Replacing the internal PSU by an external one, a lot of work. But the best solution would probably be to replace the lunchbox (sorry for the bad news).

96

First Aid / lunchbox help noise and buzz.

« Last post by Consigliere on October 28, 2025, 12:08:46 PM »

I'm finished building my AB528 and it sounds absolutely amazing. 

One thing that is weird (probably has nothing to do with this unit but) is that when I have it mounted in Bento10s it sounds fantastic but in my Bento6 (not s model) it's alot of weird noises going on. Nothing "gain related" but a constant pinkish noise and a buzz/tone sound. It's both depending on which slot in the box it is installed in (worst close to the transformer) but not constant better in the slots to further away, and also phantom power. The buzz/tone is mostly detectable with fantom power. And turning it on the sound shifts up in pitch like a spike and goes down again to aprox 185hz or so. (with an visible harmonic around 3-400 something.)

I've never heard these noises before but I only had eq's and compressors in it before. (this is my first 500 preamp)

I know I should probably ask elsewhere but I found other threads in this forum about Fredenstein Bento noise so I was hoping to se if I could get some help solving it. I want to use this bento6 for portable use. Is it a grounding issue? Transformer issue? Is it worth mod'ing or repairing? It also feels like the pcb-connection doesn't "slide in" that deep in the bento 6 comparing to my bento10s. Could that be an issue? Is it possible/worth it to try find a replacement transformer for the lunchbox, and which one in that case?

Any advice is welcome and also if you had a similar experience and how you tackled the problem. 
Thanks //Anders

97

LA502 Optical Compressor / Re: Absolutely no gain working.

« Last post by JPK on October 21, 2025, 05:15:15 PM »

Still following the signal:
How many volts do you get across R17, with the multimeter probes on either side of R17?

98

LA502 Optical Compressor / Re: Absolutely no gain working.

« Last post by justebruyat on October 21, 2025, 01:02:24 PM »

Merci de votre réponse
Oups, sorry...

Input transfo
Pin 1-5 : 2.06 kOhms
Pin 10-6 : 1.8 Kohms

With input 1khz, 1vac:

R2 right pin: 0.6v
R5 right pin : 0.3v (non 0.5v)

Gain à 0 : TP0V - TP1 : 0.3Vac
Gain  à 100 : TP0V - TP1 : 9.2v

Gain à 0 : TP0V - Pin7 U1 : 0.3Vac / 0.4Vac
Gain  à 100 : TP0V - Pin7 U1 : 14.4Vac

Bypass ou In n'affecte pas ces données

99

LA502 Optical Compressor / Re: Absolutely no gain working.

« Last post by JPK on October 21, 2025, 11:11:57 AM »

Try to follow the signal
Good on R2 and R5

How many volts on U1 pin7 ?
How many volts on TP1 ?

Cant check input transfo as my voltmeter isn't accurate enough for 2ohm
It is not 2 ohms but 2 kiloohms.

100

LA502 Optical Compressor / Absolutely no gain working.

« Last post by justebruyat on October 19, 2025, 12:23:43 PM »

HEllo,

Everything has been done as guide intended; comp. seems to be working.
Bypass let the sound go trough ....
When turned to IN, there in absolutely no VAC. out
Re soldered evrything that needed too, zero short, diodes, caps and ICs in right order.

Relay doesnt click when changing the main psu switch, then sick to this position
Only clicks when turning on / OFF the whole unit
Though seems to be working fine with an outside dc quickly applied to its coil.

I also did a mistake on desoldering C4 (i had put first wrong value of capacitor and had to change it)
Wich broke the connection of the component to the PCB on the up side. Seems perfectly ok on the down side.
I have continuity as described by the pictures.

I'm not so good at reading schematic but it seems to me this is not the issue, as i still have contuinuity to the components it's supposed to .
C4 goes to 6 and 7 (in and out b) of U1B puis 7 est lié à U1A (3) in+... etc etc...
Sauf si le potard est à zero, je ne constate aucun court circuit. j'imagine donc que ma petite erreur n'est pas trop grave. Et que le problème vient d'ailleurs.

Thank you anyone, by advance for any help.

D'ailleurs -

"Check you get no DC volts on TP1. Any DC above a few millivolts here shows that there is an issue." --- zero or .001 V, pas de problème de ce coté là

Good on R2 and R5

23omh outside beatween 2/3 pin out.
5 ohm Between 0v and TP1.

1-3  ? 10 ohms (5 ohms if in circuit)

6-8  ? 10 ohms (5 ohms if in circuit)
9-12 ? 12 ohms
13-16 ? 12 ohms

All that is checked well.
Cant check input transfo as my voltmeter isn't accurate enough for 2ohm