My D-lite is dying

[DaveBo32]

My D-lite was working great for months, Then I started tinkering with it. I started experimenting with different caps. I replaced the .0012uf cap on the bass pot with a .001uf. Everything is working just fine. Then I started to replaced the 270pf treble cap with a .002uf still working. Then I tried a 330pf. Did not care for it, went back to the 270pf. Still working,so I thought, but my PAB stoped kicking the sound up instead the opposite happened, the sound was thin. Also when I turned the volume pass 3:00, the sound would die down. I tried retapping the soldering joints. Nice back in bizz. Went to bed, next day the PAB wasn't working. I repalced the socket for V1, thinking I had a bad socket. I also sprayed contact cleaner and tighten up the sockets, Still same problem. I retapped the solder joints again, doesn't help. I tried different tubes. Crap, Crap Crap! I checked my voltages, not looking good. V1(pin1=204, pin6= 70) something is wrong here, V2(pin1=213, pin6=228). V1 and V2 look alot brighter than normal. The B+4 voltage, if I remember was 324Vdc, I think something is loading it down, but What? I at the point of tearing the board out an taking a good look underneath. I hope it's just a jumper or something that came loose. I hope it's not my PT or OT. My heater voltages are at 6.1vac, My 6V6's are biased at 19.5mVs. I need help....I just want to play...Any suggestions that would help me narrow this down before I tear the bd out would help..Thanks

[mlp-mx6]

A couple things come to mind.

It is possible that you have a leaky cap that is throwing off the voltages.

The other is that I'm wondering if in all your un-soldering and re-soldering there is a drip of solder (or a lead that you left too long) that is touching or nearly touching the chassis from underneath your board, causing a short or intermittent short. Can you loosen the board connections and look at the underside (perhaps using a dental mirror)?

Good luck!

[Ed de Jager]

After reading your story i`d suspect the 270pF you replaced the 330pF with.
The problems started when you put it there right?


Ed

[Darkbluemurder]

193V on pin 1 of V1 looks good. If pin 6 of the same tube doesn't have anything near that voltage I would suspect that one or more tone caps are leaky. Try the following:

1) Take out V1 and measure the voltages on pin 1 and 6. If they are not somewhere around 200V each then the tube is not the culprit.

2) Replace all tone caps with new ones and measure the voltages again, still without the tube in the socket. If the voltage is around 200V at pin 1 and pin 6, put the tube back in and you should be fine.

I am not sure how you wired the PAB but if the sound got thinner with the PAB engaged this can only be explained by DC getting through the treble cap with no way to leak off through the tone pots. I would make all voltage measurements with the PAB disengaged first. If they are OK check also with the PAB engaged. They should not be any different.

Good luck!

[DaveBo32]

Well, I learned my lesson the hard way. Don't cheap out on sockets and don't use alot of flux. My D-lite is up an running. The problem ended up being this green corrosion on pin 6 of my first preamp stage. I tried to clean it up with some contact cleaner, but it was beyond hope. The flux I used was a bit to aggresive. I replaced the socket with a new one with gold contacts....sweet, back in biz. Voltages look great and amp is quite as can be.

Thanks for the suggestions....

[yeahyeah]

seperate flux? what kind of solder were you using? Most people use rosin core solder wire these days, I've never heard of using seperate flux for this type of stuff.

['67_Plexi]

The problem ended up being this green corrosion on pin 6 of my first preamp stage.

Damn NE weather, ehh ???

[RJ Guitars]

DaveBo - Flux is generally used to clean and strip the outer layer of metal off of something to expose fresh new material in order to enhance the strength of a mechanical joint... like in copper water pipes or an automobile radiator. In those cases you want to get the solder onto that fresh metal and join the pieces immediately then rinse the excess flux away as fast as possible...

Of course you can't do that in an electronics assembly so that flux just keeps eating away at any metal surface it touches. The green you saw is the oxidized copper from the tabs of your tube socket. If you see any more green stuff it is pointing to a future problem.

Glad you found your problem.

rj

[skyboltone]

DaveBo - Flux is generally used to clean and strip the outer layer of metal off of something to expose fresh new material in order to enhance the strength of a mechanical joint... like in copper water pipes or an automobile radiator. In those cases you want to get the solder onto that fresh metal and join the pieces immediately then rinse the excess flux away as fast as possible...

Of course you can't do that in an electronics assembly so that flux just keeps eating away at any metal surface it touches. The green you saw is the oxidized copper from the tabs of your tube socket. If you see any more green stuff it is pointing to a future problem.

Glad you found your problem.

rj

hmmmmm. I've seen 60 year old gear with rosen flux on it and no further oxidation. I'm wondering if somebody's using acid core or acid paste/liquid flux like the plumbers use.

[RJ Guitars]

hmmmmm. I've seen 60 year old gear with rosen flux on it and no further oxidation. I'm wondering if somebody's using acid core or acid paste/liquid flux like the plumbers use.

I'd say you are right on the money there...

Now that you mention it, i recall seeing that thick greasy stuff on some real old equipment and as you say there was none of that green oxide like you get with acid... i guess i actually don't even know what "rosin is" except that it is electronics friendly. I am assuming that rosin doesn't actually attack the metal like acid does, thus no long term corrosion??

I first learned about not using acid core solder in a warning pamphlet that came with my first "HEATHKIT" guitar amp kit... that was an awful amp!

rj

[skyboltone]

hmmmmm. I've seen 60 year old gear with rosen flux on it and no further oxidation. I'm wondering if somebody's using acid core or acid paste/liquid flux like the plumbers use.

I'd say you are right on the money there...

Now that you mention it, i recall seeing that thick greasy stuff on some real old equipment and as you say there was none of that green oxide like you get with acid... i guess i actually don't even know what "rosin is" except that it is electronics friendly. I am assuming that rosin doesn't actually attack the metal like acid does, thus no long term corrosion??

I first learned about not using acid core solder in a warning pamphlet that came with my first "HEATHKIT" guitar amp kit... that was an awful amp!

rj

Tree sap. Pine, fir, that sort of critter. Also called Pitch, pine tar. Called other things too I suppose.

[heisthl]

I'm not a chemist, haven't played one on TV or stayed in a Holiday Inn Express last night - but the way it was explained to me was electrical solder has rosin core flux that cleans metal surfaces when heated and is inert at room temperature. The downside is it is slightly conductive so it needs to be removed (defluxed) if it bridges contact points.