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"Lacewood" Amp V2.0
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=5736
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Author:  mwhouston [ 24 Jun 2017, 18:51 ]
Post subject:  Re: "Lacewood" Amp V2.0

lowhifi wrote:
Yes it is polished, it was a corroded and scratched 6061T6 aluminium plate, now i can see my ugly face on it.

I guess the flip side of polishing would have been to spray. I use acid etch primer and epoxy piant all from a spry can. I have thought about polishing top plates but as yet have done it. I generally spray.

Author:  Soundbrigade [ 25 Jun 2017, 01:51 ]
Post subject:  Re: "Lacewood" Amp V2.0

To the annual VW summit in our town (http://www.vweteranerna.se/413762050), there use to be a beetle that is covered in corrosion. It looks so cool that I wanted to try to get a steel sheet covered in rust and cover the rust with clearcoat.

Author:  lowhifi [ 25 Jun 2017, 19:28 ]
Post subject:  Re: "Lacewood" Amp V2.0

I didn't spray the flip side but i remove most of the corrosion with a power sander, for the upper side i use an aluminium polish who also protect.
On an other forum one guy recommend to remplace the cathode bypass capacitors with film type capacitor because they are in the signal path,i put Elna Cerafine.

Author:  mwhouston [ 25 Jun 2017, 20:24 ]
Post subject:  Re: "Lacewood" Amp V2.0

lowhifi wrote:
I didn't spray the flip side but i remove most of the corrosion with a power sander, for the upper side i use an aluminium polish who also protect.
On an other forum one guy recommend to remplace the cathode bypass capacitors with film type capacitor because they are in the signal path,i put Elna Cerafine.



Metal film is best but it may be a big cap. Try NP electro.

Author:  john55 [ 01 Jul 2017, 10:05 ]
Post subject:  Re: "Lacewood" Amp V2.0

Suncalc wrote:
Well it sounds like you've got a bad transformer. That is really rare for Edcor. Is this the XPWR009-240?


I've just received two XPWR009-240 power transformers from Edcor. One replacement and one for the next Lacewood V.2 build for a friend. I thought I'd check these straight out of the box, on the bench, direct connection to the 225V mains with no loads. I'm reading 250V-0V-250V instead of 275V-0V-275V......5.4V instead of 6.3V and 4.4V instead of 5V. As I've stated before, I'm expecting slightly lower voltages owing to the input voltage being 6% down on the stated 240V primary winding, but not this low. I now have three of these transformers. I guess I can get around the HT being low by alterations to the Power Supply, but can I run the 6V6's and the 6SN7 on 5.4V to the heaters? Also will 4.4V instead of 5V to the rectifier valve give me problems? Does anyone have a workaround for this type of problem?

Author:  mike567 [ 02 Jul 2017, 10:37 ]
Post subject:  Re: "Lacewood" Amp V2.0

Boost transformer. 12.6 volt secondary wired in series with the primary of your power transformer will put you in the ballpark.
Use higher voltage till you get what you need.

Author:  john55 [ 02 Jul 2017, 10:53 ]
Post subject:  Re: "Lacewood" Amp V2.0

Really? I guess it would up ALL the voltages which is the ultimate solution. I was hoping that someone would say "run the heaters at 5.4V, absolutely no problem", but that would contradict pretty much everything I've read in the last few days. Also would have been too easy.

Author:  mwhouston [ 02 Jul 2017, 19:01 ]
Post subject:  Re: "Lacewood" Amp V2.0

john55 wrote:
Really? I guess it would up ALL the voltages which is the ultimate solution. I was hoping that someone would say "run the heaters at 5.4V, absolutely no problem", but that would contradict pretty much everything I've read in the last few days. Also would have been too easy.


You could rectify then regulate the heater voltage. That way you may even get a quieter amp. Just ensure the regulator will hand the total current or use two seperate regulator and filter ccts.

Author:  john55 [ 03 Jul 2017, 01:55 ]
Post subject:  Re: "Lacewood" Amp V2.0

Okay, I now have two workarounds. I'll probably try them out next weekend. Thanks to both of you. It looks like I'll have to give Edcor a miss when it comes to Power Transformers, I don't have this problem with Hammond.

Author:  john55 [ 04 Jul 2017, 02:46 ]
Post subject:  Re: "Lacewood" Amp V2.0

I've decided to go with boosting the transformer as that will up ALL of the voltages. I've found 240V-12.6V heater/filament transformers rated at 0.3A, 0.5A, and then 1A up to 4A in increments of 0.5A. I don't know how to calculate how many watts the amp draws, so I can't calculate the current. The price difference is pretty big so I don't want to overdo it and just get the biggest. Any help with this would be appreciated.

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