dna 1 recap !

[Seattlerepairhobby]

I read extra forums where DNA-1 end users received suggestions from Steve and Pat. I can resume here:

1. The original DNA-1 driver PCB had built with laminated and thin upper and lower circuits that the through holes of uppper and lower sides of laminate would separated that led to open circuit > distortion sound then worse. When this happen, do not turn it on again.

2. Some folks mentioned the ICs and drive transistor got their Pins disconnected due to delaminated as heat led to separate circuit both side of the board. Normally/originally the IC pins/component pins need to insert all the way through the via/hole before soldering.

3. Recap to keep bias stable (measure at positive output and emitter R.47ohms resistor). None recap/or after racap needs to adjust the bias current as design (depends on orginal DNA 1 or upgraded input board level (gold or black or else) from Steve.

Now I think the solution to save money and my DNA-1 are:

- Take notes and pictures for each board.
- Remove the boards to recap all capacitors.
- Spend time to remove old soldering at each pin, insert thin wire through each via/hole, then resolder that hole. That will help stopping the delaminate / disconnect from upper and lower circuit.
- Reinstall board, upgrade wires, add more GND wires, apply insulation pads, tighten properly, measure to ensure the output transistor separated with heat sinks.
- Use 0-115V AC source to slowly increase 45-50v and measure the output bias voltage. Make sure both left and right output balanced
- Re-adjust the bias output for each output board after 1 hour warm up.

I also looked at the ICs on the input board and will order them.

I also think of redesign the board with better laminate and increase vias size/add extra pin holes/vias. Then oder two set of part and build my own input and poweramp board

Any suggestion?

[admin]

Well, that certainly is a project. Lots of time and effort. But I'm sure that such a massive overhaul would kick the longevity of the unit up by a couple of decades. So I think when you are looking to undertake such a time consuming endeavor on an older (lower cost) unit, it's done out of a subjective attachment. Kind of like a classic car, you don't spend a lot of time and effort on it because of the engine power alone.

I think it's great. Could you spend less time/money and buy a newer unit,... yeah probably. But this sounds like a fun project on a piece of equipment that brings you a lot of joy. If you decide to go ahead, I would love to see some pictures of the refurb process.

[AnotherJohnson]

I agree with admin … there is no logic here, but there may be enough love. It is solely justified by attachment to the gear. The most useful possible outcome is the satisfaction of a job well done … if you’re lucky, you may also be rewarded with decent SQ.

Admin uses a car restoration analogy … this is restoration of an Edsel or Corvair, not a Porsche or Maserati. Some people choose the former. Nostalgia is a very personal thing.

[Seattlerepairhobby]

Thanks admin and AnotherJohnson. I will start to rebuild it tonight. I think I will slowly / carefully finish it within 1 week. I have all the capacitors, wires and document.

Chan

[Seattlerepairhobby]

Hello Admin and All,

Do you know where I can custom order the Toroidal transformer for Mccormack DNA1? It is117V input and multiple outputs (dual 60V. Dual 18V, dual 40V and dual 30V).

[admin]

I would be surprised if they are still selling the original OEM transformer.

Maybe trying to find something here that matches the specs: https://toroid.com They also do custom transformers but have no idea how much that would cost?

[Seattlerepairhobby]

I would be surprised if they are still selling the original OEM transformer.

Maybe trying to find something here that matches the specs: https://toroid.com They also do custom transformers but have no idea how much that would cost?

I called them to ask for the custom toroidal but no luck yet. Their website has customize ordering but I didn’t understand some input data for each output. i will call them again next Monday.

I have not touch the original DNA-1 yet. A friend from FB and maybe from here, John from Greece, said that there are difficult things to do and he advised me to upgrade capacitors from Mouser and high end resistors from MP. This upgrading might take longer than I expected.

I bought another Mccormack DNA-1 deluxe Rev-A for only $1100 plus shipping. It is still really good sound as owner mentioned. It quite old since it had low SN. I will receive it by end of this month. Cant wait to test it.

If mu DIY failed then I am thinking about send both the DNA-1 and DNA-1 deluxe Rev.1 to Steve for upgrading both. I sent an email to Steve/Pat to see how it work/solution/price.

Chan