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Post subject: Re: 93 blues deville fried diode- long winded..
Posted: Fri Feb 25, 2011 9:55 pm
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Yes, you are correct, forget TP34, it is for the reverb, I shouldn't have included that as a test point. Is there a reverb switch? :? Sounds like the switching circuit is working, next check the relays. There are a few ways to do it, this is just one way. With the amp off, pull V1 and V2 noting their positions so you can put them back in the same place. Turn on the amp, but leave it in standby, start with RY2, you will measure the resistance of the contacts while switching channels. Be aware that there will still be voltages in the amp, so only contact the parts that you are checking with the meter. Of course, this is dependent on the schematic being correct for your amp.

With the negative meter lead on the chassis, positive lead on the right terminal of the "Master Volume" pot, check the resistance. The resistance should be zero ohms on one channel, and high ohms when switched to the other channel. Next, move the positive lead to the right terminal of the "Drive" pot, and repeat the measurements, zero ohms on one channel and about 12K ohms when switched to the other channel. Then with the "Drive" pot turned all the way up, check the resistance across the two outside terminals of the "Drive" pot, it should be zero ohms on one channel, and around 250K ohms when switched to the other channel.

For RY1, negative meter lead to chassis, positive meter lead to the right terminal of the "Volume" pot, and repeat, zero ohms on one channel, and high resistance when switched to the other channel. Then, put the meter leads across C4 and check the resistance, zero ohms on one channel, high resistance when switched to the other channel. Let me know what you find. :)

And, yes you may hear the relays clicking when powering up or down, that's normal.

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Post subject: Re: 93 blues deville fried diode- long winded..
Posted: Fri Feb 25, 2011 11:36 pm
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Thanks Shim..
can I access these points without having to take out the main pcb, as it is in the cab and really the only safe way for me to power it up.?
For instance, can I use a resistor leg on the pot side for these measurements, or do I really need to be going through the pot?

With the measurement for C4, do I need to have neg of the meter on one side and pos on the other of this capacitor? I'm assuming yes.

Thanks
Rich

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Post subject: Re: 93 blues deville fried diode- long winded..
Posted: Sat Feb 26, 2011 5:44 am
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Hi Shimmilou,
well, went back and began to test a few of the TP around the relays.. starting with TP4 (R8).. checked with the clean channel and then hit the drive switch with the probe still on the resistor and yes, my drive channel sprang to life... mmmm, go figure.
I didn't have my foot switch in so put that in, and all is working fine now.

I went back and checked with a chop stick if there was some loose solder point around R8 while the drive was on and no problems here at all. :D

I'm wondering if one of the relays were stuck:?:
Might be something to keep my eye in the future.

But for now, all's finally well with the Deville.

I would like to once again thank you very much for the time, effort and extreme patience you've shown me with sorting this amp out.

I wish all the very very best!!

Kind regards
Rich

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Post subject: Re: 93 blues deville fried diode- long winded..
Posted: Sat Feb 26, 2011 8:23 am
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Hey, that's great richardo!

From your previous posts, yes I meant to take the measurements with the amp fully assembled, with V1 and V2 pulled. Yes, you can measure the pot from the resistor leg on one side, if the resistor and pot are directly connected together there. And, yes for C4, a meter lead on each side of the cap. Part of the relay shorts that C4 cap when the channel is switched. And, keep in mind that with the preamp tubes in place, there will be high voltage on all of the points that I wanted you to check the resistance, so don't try to measure those resistances with the preamp tubes installed. :shock:

But, yes it sounds like the relay is sticking, and/or a bad solder joint or trace around the relay. It could even be a bad/cracked resistor or other component in that area. You might want to get a couple of those relays to have on hand if the problem reoccurs....and it likely will reoccur (of course I hope that it doesn't happen again). A sticking relay would explain everything though, and it isn't uncommon for the relay to stick. :idea:

Glad that it is working for now! And you certainly should be intimately familiar with the insides of your amp. Enjoy!

P.S.
TP4?? As I stated before, forget about the AC voltages, you will get nothing useful without a signal into the input of the amp. All of the AC voltages test points on the schematic will be in a circle, while the DC test points are in squares. The squares are the ones that you want to use for the voltage measurements. :)

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Post subject: Re: 93 blues deville fried diode- long winded..
Posted: Sat Feb 26, 2011 7:11 pm
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Hey Shim,
all good advice.
Especially removing the preamp tubes when testing ohms :shock: That's what I was thinking, but isn't there power through these places.... using meter in ohm mode... eeek. been there before.. now it makes sense about how the preamp tubes work in the circuit.

Am going to definitely take your advice and get some of those 24vdc relays.
I'll probably replace both of them so that I'll feel confident about putting everything back and replace the back panels.. hopefully to play and forget for a while!
If these were indeed the prob in the beginning, which from your experience were more than likely the culprit, it will be worth my while to do so.

But all in all it's been a great learning experience, especially now that the amp is back working well. I think I know this amp pretty well now :P .
Have been playing it all morning and with the new caps and valves, my drive channel is a hell of a lot more usable... so this is a big plus and gives me more variation to my rig.

Thanks all so much again!!

All the best
Rich

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Post subject: Re: 93 blues deville fried diode- long winded..
Posted: Sat Feb 26, 2011 8:10 pm
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That is great news! Take time to congrat yourself, while shreading the stucco off your walls. With those better quality lytics installed, you are looking at potentially years and years of coinsistent good service. I've replaced several DRRI with quality lytics and you couldn't pry the amps from the owners with a crowbar.

OT: reminds me of an old, tired joke. " Fire Island Prison. Where they separate the men from the boys... with crowbars. " :shock:

Good job! Enjoy your work.


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Post subject: Re: 93 blues deville fried diode- long winded..
Posted: Sun Feb 27, 2011 3:59 pm
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Lol BMW.. ...ouch!!

Yeah, lucky I live on a large block, I have had the thing up to '4-5', which is usually stage volume...(who the hell play it over this, they must be really deaf) am finding a far better range with tone, bass and middle now.
Changing the voicing now produce some great break up with tone turned down, middle adjusted and tone dialed further around gives some good head room for loud clean.
Am also finding far better range and variation from the strat... while I love the bridge/ middle pickup position, I'm loving the middle/ neck even more now.

I think you're definitely right with putting decent capacitors in these things, I'm sure the valves are helping as well, although I am still a bit sus on one of the power tubes out of the new set I received... it does rustle a little bit so might buy another matched pair and see what goes.

any way, the amp is sounding so warm and thick, you can almost cut the air with a knife... I'm in love all over again with this amp. It actual is sounding more like the original Bassman, as I can remember from a previous band mate who was a Stevie Ray Vaughn purist... always wondered how he got that sound..

Thanks again for all your help as well BM....

Now I need to get my Strat a fret job... :roll:

Always some thing!

All the best
Rich

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