Starting a D'Lite

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ToneMerc
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BN Voltage

Post by ToneMerc »

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dreric
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Re: Starting a D'Lite

Post by dreric »

TM

Thanks, hadn't thought to look at Brown note.

I measured the voltages throughout the power supply and across the board and everything measure about 25% of what it should. IOW, what should be 100 volts measures at 25.

I'm using a Edcor transformer which has the primaries putting out 320 volts on each side 640 total. I'm not sure what the brown note transformer specs are and I can't seem to find them on their page.

Please correct my logic where I'm mistaken. If everything is measuring at 25% percent of what it should:

Then my power transformer is not the right spec. and or

The power resistor (10 watt 300 ohm ) is too large?

Eric
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angelodp
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Hope this helps

Post by angelodp »

Perhaps this will help

[IMG:850:1093]http://i260.photobucket.com/albums/ii9/ ... 16EX-1.jpg[/img]
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dreric
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Re: Starting a D'Lite

Post by dreric »

I think I'm tracking down the problem.

The AC from each side of the power transformer taps measures at 350.

The DC after the rectifiers measures at 105 volts.

I used 1N4007 as called for.

I did add .01 mf @ 1 kv snubber caps between the diodes, could this cause the drop in voltage?

Eric

I did find some transformer specs over at brown note and theirs seems to be 325 - 325.
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Guitarman18
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Re: Starting a D'Lite

Post by Guitarman18 »

dreric wrote:
The AC from each side of the power transformer taps measures at 350
If you are getting 175-0-175 (350v ac) going into your rectifier then that is the issue.
The DC after the rectifiers measures at 105 volts.
If you're measuring from ground to each leg (ie 350-0-350) then that is absolutely fine. You should get in the region of 460v out of the rectifier, so therein lies a problem!

I used 1N4007 as called for.
1N4007 are standard, but it sounds as though yours are fried.
I did add .01 mf @ 1 kv snubber caps between the diodes, could this cause the drop in voltage?
This shouldn't be an issue, but I would test your rectifier without them in place. Make sure the silver bands all point towards the rear of the chassis.

One other point I would have to make is that from the picture you have posted, I can't see a backing board on you rectifier/relay supply board. If you haven't got one, I'd be EXTREMELY nervous about using that amp.

Hope this helps.

Cheers,

Paul.
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Structo
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Re: Starting a D'Lite

Post by Structo »

Yes if you used the BN transformer it is like what Angeldop posted.

Double check the diodes and wiring, make sure the bias circuit is reverse polarity and make sure it isn't shorting to the chassis behind the board.
Tom

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angelodp
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backer board

Post by angelodp »

The Dlites do not have a backer board on their rectifier supply. The standoffs are sufficient to space the jumpers away from the chassis.

a
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ToneMerc
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Re: Starting a D'Lite

Post by ToneMerc »

dreric wrote:
I did add .01 mf @ 1 kv snubber caps between the diodes, could this cause the drop in voltage?

Look no further than the HV board for starters.........350VAC in, 105VDC out.

Snubbers should be connected across each diode, not in between them.

TM
Last edited by ToneMerc on Sun Apr 11, 2010 12:42 am, edited 2 times in total.
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Structo
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Re: Starting a D'Lite

Post by Structo »

It looks like he does have them across the diodes.

Hopefully the standoffs on the rectifier board are tall enough to keep the board from shorting on the chassis.

If your PT is 320-0-320 that should work fine, just 5v less than the D'Lite PT.

The stock PT has a 45v bias tap.

So you will need more resistance there to bring that down.

I would try a 1.5K 2w resistor.

I can't see the polarity of the bias diode but that also needs to be reversed with the band towards the bias resistor since it is negative voltage.

Also the stock bias cap is 100uF 100v, so you will need that bias cap to be at least 200v or bigger to handle the higher voltage.

What is the negative bias voltage you are getting to the bias pot?

As far as not getting any signal, do you get any pops through the speaker when probing the PI plates or other test points?

Double check your V1 and V2 cathode bypass grounds.

A lot of people missed those because on the first layouts those grounds were not drawn on the layout.
Tom

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kd
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Re: Starting a D'Lite

Post by kd »

My guess is it's fried rectifier. Be carefull when you solder the diodes to the board, a little to much heat will ruin the diode. Use a heat sink on the lead or be quick about the soldering process and do not overheat the diode.

Ken
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Deric
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Re: Starting a D'Lite

Post by Deric »

What are the specs on your PT? I don't "see" a diode for the bias supply in your pics....doesn't mean it's not there... :D just don't see it. The 160v bias tap seems odd....

:?
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dreric
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Re: Starting a D'Lite

Post by dreric »

Thanks for all the feedback.

Still trying to get the rectifier in working order. I removed the snubbers, changed out all the diodes 1n4007s, used a heat sink, still

350 volts AC on each side of the diode chain. Still, 98 volts DC comming out of the end. The connection to the 10 watt 300 ohm power resistor is ok, no shorts. No shorts anywhere on the power supply board. I'm perplexed.

Do diodes go bad with age? These are coming from a pack I got about ten years ago. Is there a way to test them. They seem to be working in the other parts of the amp (bias and relay PS) but those are lower voltages.

Eric
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ToneMerc
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Re: Starting a D'Lite

Post by ToneMerc »

Just so we are on the same page is the HV board wired as such and the the diodes orientated as shown?

TM
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dreric
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Re: Starting a D'Lite

Post by dreric »

The diodes are in the correct position (checked about 10k times)

Eric
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Bob-I
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Re: Starting a D'Lite

Post by Bob-I »

dreric wrote:350 volts AC on each side of the diode chain. Still, 98 volts DC comming out of the end. The connection to the 10 watt 300 ohm power resistor is ok, no shorts. No shorts anywhere on the power supply board. I'm perplexed.
Diodes don't go bad with age, but they do go bad with static. Based on this post I'd say you have bad diodes. Get a new batch and replace them.

Another test you can do is to use only 2 diodes. Connect the first 2, disconnect the rest and bridge them together. If you're still getting only 100V then the diodes are bad.
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