Mezmerize DCB1 Building Thread

[lpm76]

Dont know if I was the only one who was slight confused about the different iterations of the board.

Anyways, the bom for 4.2 is here, and I think it is the right one.

http://www.diyaudio.com/forums/blogs/tea-bag/173-old-style-dcb1-information.html

 

[Horio]

Second 100uf cap becomes small MKP type cap of .2 or .1uf, make sure it fits.

Tea-Bag, on the DCB1 Blue Hypno BOM, it says to use a film cap between 0.1uf and 10uf. How does the value of this capacitor influence the circuit? I found 0.1uf WIMA caps from Mouser with 5mm lead spacing.

Thanks

 

[Tea-Bag]

Horio,
Let me correct myself first, it's the first cap that gets replaced, not the second.
Technically I am not positive what the differences are. Both are bypass caps for the IRFP Voltage Reference. The film cap seems to offer better sound. I would buy both and try both.

 

[Nikon1975]

Looks like the board is slowly getting populated.
Unfortunately I managed to get a bunch of 100 perfectly matched let at 1.84 V, there is no way of putting them together to make 9V.

I am using the method suggested by Salas for matching, using the jfet as a current source. For this I assume that the battery voltage should be greater than 9 V. I am using 12V. Is it correct ?

A silly thing that happened assembling this board is the following: I recently got an LCR meter, capable of measuring also ESR. So I bought two capacitors, a Nichicon Fine Tune bla bla 100 uF and some surplus cap. The Nichicon costs 20 times more than the other.
If I measure them, the Nichicon are closer to 80uF and have 0.7 ohm of ESR, the others are around 95uF and 0.4ohm ESR.
What would you use ?


Best Regards,

Davide

 

[Nikon1975]

By the way, I am using one 10 ohm 3W resistors (wirewound) to set the current. I expect to have around 300mA. Is it OK ?

THX,

Davide

 

[Salas]

More like 200mA with 10R usually. Use the 0.4 ESR.

 

[AndrewT]

if the 80uF is outside specification, send it back and demand refund.
Or Demand refund and let them collect if they think them worth retrieving.

 

[Horio]

I'm planning to hot-rod my DCB1, and I'd like to run it at 600mA (3.3ohm resistors). I'm planning bolt the MOSFETs to a custom chassis with a 6mm thick bottom panel. The board layout doesn't really allow for mounting the rectifier diodes to the bottom panel. Do you think I could get away with running it at 600mA if I put some of these on the MUR820's I have? It isn't much, but I could bend the fins out to create a flat heat-sink.

 

[Tea-Bag]

You've got the right idea, there is not much space if you mount the TO-220's there.
If you can't get those sinks to bend that way, and my experience is that alum is not too pliable, I would use some of the 6mm chassis and 4/40 tap and just add some surface area to it.

 

[johnm]

Can the mosfets not just be desoldered, and instead mounted to the underside of the board (so bending the legs UP to fit the PCB)? I would have thought that would then easily allow it to be mounted to the chassis base, and allow that to be used as the heatsink?

- John

 

[Marra]

Can the mosfets not just be desoldered, and instead mounted to the underside of the board (so bending the legs UP to fit the PCB)? I would have thought that would then easily allow it to be mounted to the chassis base, and allow that to be used as the heatsink?

- John

This is exactly what I did with my Blue Hypno; the 6mm bottom plate barely gets warm.

 

[johnm]

This is exactly what I did with my Blue Hypno; the 6mm bottom plate barely gets warm.

Ah my mistake actually - I believe he's talking about the rectifier's being the problem to mount underneath rather than the mosfets. That'll teach me to post too fast

 

[Marra]

Ah my mistake actually - I believe he's talking about the rectifier's being the problem to mount underneath rather than the mosfets. That'll teach me to post too fast

You're right John; missed that too.

 

[Nikon1975]

Japan is a funny country: you can buy Toshiba jfet at the grocery store, but if you ask for a BC, they look you like an alien. I forgot to add BC517 to my mouser order, I have BC550 and BC560. Can I replace the 517 with something else? what are the important parameters for this part?

Thanks,

D.

 

[Tea-Bag]

We got some osciallation on the relay's originally with two BC546's in the prototypes last year in some cases. a .15 cap used (I forgot how) can solve it if it occurs.

The BC517 solved that problem. You'd hear it if it occurs, the board will make a 'hiss'.

 

[Salas]

Japan is a funny country: you can buy Toshiba jfet at the grocery store, but if you ask for a BC, they look you like an alien. I forgot to add BC517 to my mouser order, I have BC550 and BC560. Can I replace the 517 with something else? what are the important parameters for this part?

Thanks,

D.

The current gain is important. Must be a Darlington. Else use that 150nF between C,B of the normal BC5xx you got. Use a small film cap and patch at board's underside.

 

[Nikon1975]

For the led strings, is it important to match them exactly at 9 and 5.4 V or is more important to match the + and - side ? My leds are very consistent at 1.82, so I have no problem to match + and -, but hard time to get below 9.3 V.

(
Thanks,

D.

 

[Salas]

Don't worry much. You are in a good frame. The supplies are manipulated for a certain ratio of current offset in the reference strings in the Mez anyway. Vo will never match. That is in hot rod Hypno only.

 

[prooptiki]

I am going to build a hotrod version by using two boxes one is for the transformer, so my problem is the way to transfer power AC or DC?

Using DC
transformer >>> rectifiers >>> a big cap of 22000uf (I have alot of them...cheap rubicon)>>> cable 1m >>> one 4700uf (or another one 22000uf?)>>> DCB1
Is this a good configuration?
thanks

 

[AndrewT]

so my problem is the way to transfer power AC or DC?

feed smoothed DC between the two boxes arrangement.