Anyone on the forum have a Dodd MLP?

BlueMDPicker

If so, I need some voltage measurements for the external PS. My PS has failed and I want to build something to replace it. Thanks!

BTW - tried Gary for the info but that didn't produce results.

BlueMDPicker

*bump*

george daniel

I know that Tom(trietz) has one--pm him--he knows his way around with a vm.

marvda1

gary is in the hospital. http://www.audiocircle.com/index.php?topic=121282.0

BlueMDPicker

george daniel wrote: »

I know that Tom(trietz) has one--pm him--he knows his way around with a vm.

Thanks George. Will do. Just trying to determine what voltages Gary was delivering with the PS.

BlueMDPicker

marvda1 wrote: »

gary is in the hospital. http://www.audiocircle.com/index.php?topic=121282.0

Thanks for the link! Hope all goes well with his health issues.

BlueMDPicker

*Bump*

I'd like to try to get this preamp operational again. So, asking if anyone here who owns an MLP, and is comfortable with a VOM, could get voltage readings from the wiring exiting the power supply board. Thanks!

george daniel

I will call Tom,, he has one that I sold him,,and he knows his way around with a vm

BlueMDPicker

Thanks George!

SCompRacer

Hey George, he doesn't need a vm. Just a shot of his facial expressions as he touches stuff will tell us if it's hi or low..lol

george daniel

Could not resist Rich

SCompRacer

george daniel wrote: »

Could not resist Rich

OUCH! I remember this! Oh, the horror!

pumpkinman

Is this Rich ??

lightman1

Tom called me after this happened.
It was like he was in denial. Shock.
Nearly catatonic.

treitz3

Wow, I knew I spent some time off of the forum but I missed this how? Mike, I'd be glad to help you. What are you interested in finding out?

That photo hurts still. *sighs*

BUT it did get push me to get the speakers that I have now. The crossover upgrades for them should be done soon. *prays*

Tom

BlueMDPicker

Hi Tom,

With no schematic available, the path I'm leaning toward is an entirely new power supply. It would be great to know what the external transformer tap voltages are. And, I'm interested in the voltage readings on the following points on the internal power supply/regulation board (left to right) pictured below:

Red/Black
Orange/Orange
Red/Red
White/White
Black
Red/Red
Blue twisted pair
Red twisted pair

treitz3

I take it that this board resides in the main unit and not the power supply?

Tom

BlueMDPicker

Tom,

Yes, it's the upper right hand board in this full chassis view.

megasat16

Blue,

Make sure you discharge those Filter caps before you touch on the board. I have some not so fond memory of letting the 250V DC pass trough my hand a few times I forgot to do that. Thanks God it's only through the hands and not my heart.

Anyway, what's wrong with the unit when you said it's the power supply problems?

It's not so clear that it's the diode or the enamel coated resistor but from the picture, it's possible it is the diode that looks like fried. The diode has the color band marked for cathode. When it's overheated or over worked, the color band usually kind of fades away. It's the first one on the lower left. Can you tell me is it a diode or a resistor? If it's a Diode, remove one end and measure it with the DMM in the Diode setting.

BlueMDPicker

Hi @megasat16

Thanks for the sage safety advice. I do practice safe practices with capacitors at all times.

The photos are of the original board components. After Gary had it and it was still cremating the warm-up delay relay in the external portion of the PS, I bought new resistors, diodes, caps, transistors and replaced everything you see (and everything you don't see in the external, transformer chassis). Still blows the relay instantly when power is applied.

After the time/money spent trying to diagnose a circuit without a schematic of any kind and no test point info, I am truly "over it". I want to determine the voltage and current demands of the tube rails primarily and build an entirely new PS--perhaps even nicad battery based. I need someone with a working MLP to, hopefully, get me on that path.

Thanks again!

megasat16

Is it blowing fuse also? IS there a fuse for the Primary side of the (external?) transformer at a minimum? Does the fuse blow?

I don't quite understand how the relay is fried instantly. The relay may be used on the primary side in addition to the fuse. But if the relay is blowing up on the primary side, it's quite a sight to see the contacts shizzles and burn out. If the primary side relay is blowing, the primary of the transformer is shorted. If the relay is on the secondary side of the transformer, a lot more voltage than the correct voltage has been applied to the relay. You should be able to power up the external power supply without hooking up to the unit. I can't say for sure without the schematic or seeing the innards of the power supply but it's very possible that the power supply should be powered on and the voltages should be measurable on both sides of the transformer without any fuse blown or relay fried (since there is no load connected to the transformer). Readings are just for the open load transformer voltages which is a bit more than the loaded voltage.

txcoastal1

@BlueMDPicker
Blue, have you tried emailing Danny Richie, to see if he might be holding some of Gary's designs/schematics?

BlueMDPicker

megasat16 wrote: »

..... I can't say for sure without the schematic or seeing the innards of the power supply but it's very possible that the power supply should be powered on and the voltages should be measurable on both sides of the transformer without any fuse blown or relay fried (since there is no load connected to the transformer). Readings are just for the open load transformer voltages which is a bit more than the loaded voltage.

All very plausible. But, absent a schematic and the entire rig point-to-point wired, it's really difficult to map your way through his intent. This preamp has been down for over 4 years, been to Gary, been to the most highly regarded hifi tech in my area (no cigar) and, as I mentioned above, I'm ready to move on to another PS that I DO have the schematic for. I do appreciate your thoughts on it, though.

BlueMDPicker

txcoastal1 wrote: »

@BlueMDPicker
Blue, have you tried emailing Danny Richie, to see if he might be holding some of Gary's designs/schematics?

@txcoastal1

I don't know Danny. Could you PM me some contact info? Thanks!

txcoastal1

LOL...I just sent Blue the same info 2mins ago

I guess that's what happens when you don't refresh

megasat16

BlueMDPicker wrote: »

All very plausible. But, absent a schematic and the entire rig point-to-point wired, it's really difficult to map your way through his intent. This preamp has been down for over 4 years, been to Gary, been to the most highly regarded hifi tech in my area (no cigar) and, as I mentioned above, I'm ready to move on to another PS that I DO have the schematic for. I do appreciate your thoughts on it, though.

Gary didn't / couldn't fix his own design and build when he was alive? It is telling something like it could have been a prototype build but I am sure it's very fixable and minor design problems might have been corrected some time later which you seem to have the schematic for.

If you want to post pictures of the Power supply unit, I will see if I could provide some opinions on it. But need to see both sides of the boards (solder side and component side) of each unit.

BlueMDPicker

@txcoastal1 & @DSkip

Danny was very responsive to an email sent this morning. Thanks again for the contact info! However, my quest continues. Thought this info might be of some service to other Dodd Audio owners moving forward:

Hey Michael,

I am sorry to hear about your troubles. I do have some schematics on Gary's later stuff, but don't think it includes anything on this unit.

A good friend of Gary's has been handling some of the repairs on his gear since Gary passed. He is very good with it and should be able to take care of the problem for you.

Contact Charlie Cocci at 508-588-8389

Thanks,
Danny

treitz3

Hey, Mike. I haven't forgotten about you at all. Life keeps getting in the way man. Just wanted to let you know.

Tom

BlueMDPicker

Hi Tom,

No worries at all here. I appreciate everyone's help!

Mike

MrBuhl

I have an MLP and a multi meter, but I don't know my way around the multi meter or a circuit board. If you can explain what to do, I'm game to try!

BlueMDPicker

Thanks! But, the very LAST thing I want to happen is for someone to possibly cause damage to their preamp. Much appreciated though.