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PostPosted: 30 Nov 2009, 21:33 
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Hi guys, I got a review of my OddWatt 5751 SRPP / KT88 Monoblock Tube Amplifier Kits on the site now. I'm really pleased with the kits.

Cheers

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PostPosted: 01 Dec 2009, 21:02 
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Joined: 14 Oct 2008, 17:35
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Location: Dartmouth, Nova Scotia
Those sure look nice Gio, they remind me allot of the Heathkit W5M mono blocks.... I have a pair sitting in my basement with their outputs pulled off them to be used on my massive Williamson amplifier.

I can see potential to turn them into Odd Blocks but they have a CT of over 900V!!!! :hot:

I am getting to the point where I really need to just save up and get one of these kits because I have had very little luck with building projects from scratch lately, especially when some of them require more time than I have these days. :wizard:

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PostPosted: 19 Oct 2010, 20:14 
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I had one of the earlier kits and I recently upgraded one of the monoblocks. The new versions of the kit come with a different transformer with a lower V filament tap. This eliminates the voltage dropping diodes which ran pretty hot. The LM317 is on a larger heat sink so it runs cooler now. The timing circuit was also changed. It now uses a 555 timer and the turn-on delay is set at 60 seconds. The grounding scheme also changed. I'll update the review page in the next little while.
Cheers

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PostPosted: 26 Oct 2010, 16:52 
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Joined: 03 Jan 2009, 10:44
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Hello, Gio,
It's time for me to finish my DIY Odd Blocks, and I am most interested in the new timing circuit you mentioned. I did not incorporate a timing circuit in my build but installed two power switches; in hindsight this was not a bright idea when better options exist.

I also happen to have some 555 chips sitting around...

Is it possible for you to describe the circuit, or point me towards another source? Many thanks!!
Lofton


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PostPosted: 26 Oct 2010, 19:37 
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There is some info starting here: viewtopic.php?p=10739#p10739

Sorry, no progress on my end.

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PostPosted: 28 Oct 2010, 00:17 
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Thank you, Gio. The lead was helpful. Curious though, about what relay should be used in terms of ratings or even source. Guidance would be appreciated.
Lofton


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PostPosted: 30 Oct 2010, 13:15 
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Hi Lofton,

I've got an email in asking for permission to post the new schematics.

The relay that came with my kits is a OSA-SH-212DM5 (5A 240VAC)

Cheers

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PostPosted: 01 Nov 2010, 11:09 
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Thank you, Gio,
I'll tinker with drawing something up and will post it for comments.

Meanwhile, getting update schematics would be really great so I can start rebuilding my amps before I finish building them...
Lofton


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PostPosted: 19 Nov 2010, 12:04 
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Location: Arizona, USA
Hi Everyone, A number of questions have come up on the relays. As probably most of you have discovered, it is difficult to find any relays rated at the B+ voltages used. Very expensive and very large. It turns out that the relatively common ones work fine. The ones in my reference amps (the original project ones - with all the upgrades) have functioned fine for over two years. So, go for the OSA-SH-212DM5 or similar spec ones. Even though it seems as if they should fail immediately, they don't.

Good listening
Bruce

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PostPosted: 19 Nov 2010, 12:39 
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Joined: 06 Jun 2008, 20:12
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Location: Houston, TX
Bruce have you considered mosfets as switches?
You could use just about any transistor but for instance this optomos is designed specifically for 400V and 250mA. Now, current might be to low, not sure, but this is just one example. PLA140 Relay

Uriah

EDIT: Dont think my example part would work at all but still its an idea because mosfets can be used as ON/OFF switches. I did a search on mouser for Drain/Source voltages higher than 400 with ability to handle more than an amp and there are several choices.

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