CLM Dynamics DB500S Expounder

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R

Rowboat

Well-known member
Joined
Jul 17, 2022
Messages
47
Location
Philadelphia
Some time ago a CLM Dynamics DB500S Expounder came my way in non-functional shape.

The toroidal transformer was detached from its mounting point, though its wiring was still connected. The numerous boards appeared undamaged.

A thorough search for Allan Bradley, the Expounder's designer and former owner of CLM, came to nowt. Likewise, the company in Aberdeen that did CLM's assembly has vanished.

I reached out to PMI (they now own Trident), reasoning that since [ed. 'the other'] Alan bought out CLM to obtain its patents, PMI/Trident would surely have a schematic for the Expounder.

This made sense, as PMI used Allan Bradley's patent to design the Trident Hi-Lo dynamic equalizer.

The PMI tech with whom I corresponded told me that he didn't have a schematic for the Expounder, and wouldn't risk a repair attempt.

A tech in Watertown MA was recommended by a fellow Gearslut, so the CLM DB500S was duly consigned to his outfit, Audio Proz.

Seven months have passed, with no evidence of any progress on the repair.

Do any of you perhaps
a) possess a schematic, or
b) know of a professional tech who has worked on the DB500S?

At this point, I'm ready to admit defeat.

Best regards,
Rohan
 
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To repair a product without schematic you need to reverse engineer (draw) your own schematic. As long as semiconductor part numbers and component values are not concealed you can often find the faulty components.

#1 we can ASSume the product was once working properly (I ASSume) so the design was operational.

#2 First step is to suss out power supplies. A) are voltages present, B) are voltages appropriate. If you can read active device part numbers, this can inform typical PS rail voltages.

#3 Can you identify any specialty ICs? Typically special funtion ICs have comprehensive app notes that will suggest typical circuits.

#4 General purpose active devices like transistors or JFETs, have typical junction voltages that can be checked to reveal linear operation or not. GP op amps should have predictable output voltages based on input voltages as feedback network values.

#5 be prepared to learn a bunch.... or not.

JR
 
JohnRoberts said:
To repair a product without schematic you need to reverse engineer (draw) your own schematic. As long as semiconductor part numbers and component values are not concealed you can often find the faulty components.

#1 we can ASSume the product was once working properly (I ASSume) so the design was operational.

#2 First step is to suss out power supplies. A) are voltages present, B) are voltages appropriate. If you can read active device part numbers, this can inform typical PS rail voltages.

#3 Can you identify any specialty ICs? Typically special funtion ICs have comprehensive app notes that will suggest typical circuits.

#4 General purpose active devices like transistors or JFETs, have typical junction voltages that can be checked to reveal linear operation or not. GP op amps should have predictable output voltages based on input voltages as feedback network values.

#5 be prepared to learn a bunch.... or not.

JR
Click to expand...
I know of only one chap who has successfully reverse-engineered a DB500S.

From recollection he is located 'somewhere in Eastern Europe'.

Factually, I'm out of my depth - no kit whatsoever, nor electronic skills beyond wiring houses (and building them), or monitor cabinets/crossovers, which is dirt simple.

Like you, I ASSume very little beyond my own lack of knowledge.
 
JohnRoberts said:
I gave you a logical path to proceed. If not you, find a willing technician.

JR
Click to expand...
Indeed. Hence my post concluded with a qualifier.

As noted, my Expounder has been some hundreds of miles away 'for repair' since last December.

I therefore cannot begin to troubleshoot.
 
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I have a expounder. In all my years owning it, the only servicing it needed was capacitor replacement as it runs hot.
Is there something specific you or your tech have a question about?
 
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Rowboat said:
Indeed. Hence my post concluded with a qualifier.

As noted, my Expounder has been some hundreds of miles away 'for repair' since last December.

I therefore cannot begin to troubleshoot.
Click to expand...
Hmmmm.... then I would recommend that as a first step you try to get your Expounder back (or you wait until the technician finds some time and/or pleasure to have a look at your Expounder).

Looking at the guts I have found online I cannot see anything special - like goop or sanded chips - what a SKILLED technician wouldn't be able to handle....(even without a schematic and/or experience on the DB500S).

And when I write "SKILLED technician" I mean a skilled TECHNICIAN and not a wannabe-technician-solder-jockey.
 
most chips in there are the typical tl072/74, 5532/32 variety. About the only thing that maybe be difficult is the VCA's for the dynamic tracking on the filters the rest including the pots can either be found or a substitute can be had.
 
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About all I've distilled from a litany of excuses is that the Audio Proz guy thinks there's an issue with the power supply. I think it's time to get my gear back, repaired or not.
 
To be honest, he's been both evasive and perversely rude.

As in barking batshit crazy screaming and bellowing soon modulating into self-pitying whining..

Nothing coherent has come from him about my Expounder - just a repetition of what I already knew: that the transformer was loose inside the box, that there have been prior repair efforts, that it doesn't power up, and doesn't have a blown rail fuse.

I knew that before I sent it to him!
 
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I shall contact the tech tomorrow, and ask him to return my gear. I will let you know when it is back in my possession.

Thank you!
Rohan
 
Post script:

The only other DB500S Expounder I've spotted over the past year was owned by Gregor Zemljic in Ljubljana. It has since been sold, but I have written to ask if he has a schematic.
 

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