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Link555 30 April 2020

This 900a Series is in to get TRS jacks in to replace the terminal connectors. I made a Custom PCB to replace the board mount terminal connector and reuse the original metal work with a 3D printed mounting plate.


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Boswell Thu, 05/14/2020 - 08:00

Ah-ha, the old TO-127 package! It looks like the middle 4 Darlington transistors are in this package mating with the 0.156" connectors. The outer two regulators are conventional TO-220, going directly into 0.1" sockets.

Easy to take apart, but it's a very unreliable way of connecting to power device leads. Any increase in contact resistance through ageing can quickly build into a run-away failure.

GavinO Fri, 10/07/2022 - 13:13

Hi everyone. I’m brand new to this forum. What a great post this is. 
 

I picked up a “brand new” 900 series chassis and on switch on found that some idiot had replaced the toroidal and swapped wires on the voltage selector switch, so fried the toroidal and the PSU board. Whilst I’m sure it’s salvageable, I got to wondering if I should build an external PSU using new switch modes or linear PSUs. My concern is that such modern supplies may introduce noise into the analog circuitry of the modules, but of course I don’t have enough experience for this to be any more than a thought. Im wondering if anyone has experience with such an approach?

 

Link555 Fri, 10/07/2022 - 14:17

GavinO wrote:
Hi everyone. I’m brand new to this forum. What a great post this is. 
 

I picked up a “brand new” 900 series chassis and on switch on found that some idiot had replaced the toroidal and swapped wires on the voltage selector switch, so fried the toroidal and the PSU board. Whilst I’m sure it’s salvageable, I got to wondering if I should build an external PSU using new switch modes or linear PSUs. My concern is that such modern supplies may introduce noise into the analog circuitry of the modules, but of course I don’t have enough experience for this to be any more than a thought. Im wondering if anyone has experience with such an approach?

 

Hi GavinO welcome to the forum.  Personally I would stay with the Linear power supply as it is easier to get a lower noise solution.  But it will be likely a be more expensive than an offline switcher because of the toroidal transformer.  If you need help with it let me know.  All the best.

GavinO Sat, 10/08/2022 - 01:03

Link555 wrote:
Hi GavinO welcome to the forum.  Personally I would stay with the Linear power supply as it is easier to get a lower noise solution.  But it will be likely a be more expensive than an offline switcher because of the toroidal transformer.  If you need help with it let me know.  All the best.

Link555

thank you so much for your reply. I managed to find some suitable Linear supplies from Bel Power, but to get the two down here in South Africa is about $350 so I could just as well pick up a used chassis online for the same money.
 

So I’m kinda torn as to which route to take. Maybe I should get another chassis for short term use and take my time fixing the damaged PSU? Whilst this sounds like the obvious route to follow, I’ve read comments on another forum about the added value of having some power headroom available in the case of a fully loaded chassis. 
 

Gavin

Link555 Mon, 10/17/2022 - 09:31

Link555

thank you so much for your reply. I managed to find some suitable Linear supplies from Bel Power, but to get the two down here in South Africa is about $350 so I could just as well pick up a used chassis online for the same money.
 

So I’m kinda torn as to which route to take. Maybe I should get another chassis for short term use and take my time fixing the damaged PSU? Whilst this sounds like the obvious route to follow, I’ve read comments on another forum about the added value of having some power headroom available in the case of a fully loaded chassis. 
 

Gavin

Sorry I was under the impression you wanted to repair the stock power supply rather than replace it, depending on the Damage that might be a cheaper option.

 

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