Search found 105 matches

by mrn1ngstr
Sat May 19, 2018 4:17 pm
Forum: Trainwreck Discussion
Topic: Silicone conducting?
Replies: 60
Views: 8031

Re: Silicone conducting?

Took off the flyback diodes and the crackle stopped. I'm going to replace them and if it starts doing it again, Ill just take them out altogether.
by mrn1ngstr
Sat May 12, 2018 8:50 pm
Forum: Trainwreck Discussion
Topic: Silicone conducting?
Replies: 60
Views: 8031

Re: Silicone conducting?

Solved part of my problem. The signal isn't moving up and down now, but the output still looks like crap. Back to the drawing board...
by mrn1ngstr
Thu May 10, 2018 9:57 pm
Forum: Trainwreck Discussion
Topic: Silicone conducting?
Replies: 60
Views: 8031

Re: Silicone conducting?

I didn't get a chance to test my theory last night, but I will this evening. Rocket, I feel like its two separate issues. Heres why I think that- the presence pot doesnt crackle when I turn it. Its more like a heavy, distinct rubbing that is independent of the crackle. The crackle corresponds with t...
by mrn1ngstr
Wed May 09, 2018 11:41 pm
Forum: Trainwreck Discussion
Topic: Silicone conducting?
Replies: 60
Views: 8031

Re: Silicone conducting?

I replaced all the pots last night. I was going to do it anyway because I did have a couple that had dead spots. That wasn't it though. However, I think I might have found the problem (finally). I was scoping around some more and just on a hunch, I stuck the probe to the ceramic tube socket on the P...
by mrn1ngstr
Tue May 08, 2018 2:50 pm
Forum: Trainwreck Discussion
Topic: Silicone conducting?
Replies: 60
Views: 8031

Re: Silicone conducting?

Interesting... Id like to get rid of this. So far Ive replaced the rectifier diodes, bias diode and the 220K resistor between them. It sounds better but still not great. Running an 80Hz sine wave through it, the signal is still moving up and down the Y axis a pretty good bit. There also still crackl...
by mrn1ngstr
Thu Apr 19, 2018 11:55 pm
Forum: Trainwreck Discussion
Topic: Silicone conducting?
Replies: 60
Views: 8031

Re: Silicone conducting?

Input
IMG_9236.JPG


Output
IMG_9230.JPG


Input and output overlaid- the camera caught them mid trace but you can see things don't look good.
IMG_9239.JPG
by mrn1ngstr
Wed Apr 18, 2018 10:00 pm
Forum: Trainwreck Discussion
Topic: Silicone conducting?
Replies: 60
Views: 8031

Re: Silicone conducting?

I started a new class and Ive been really busy, so I haven't had much time to work on this, but I managed do some looking around with my scope and Im seeing some troubling things. The signal looks fine coming in, but after the first stage Im noticing the signal intermittently moving up and down the ...
by mrn1ngstr
Thu Apr 05, 2018 2:17 pm
Forum: Trainwreck Discussion
Topic: Silicone conducting?
Replies: 60
Views: 8031

Re: Silicone conducting?

Ive been looking at this all wrong. Its not DC on the grid that would be a problem. It would be a problem if the DC on the grid was positive relative to the cathode- which its not. I was ignoring that and just looking at the presence of the voltage. Duh. :oops: Which will probably put my problem els...
by mrn1ngstr
Thu Apr 05, 2018 12:36 am
Forum: Trainwreck Discussion
Topic: Silicone conducting?
Replies: 60
Views: 8031

Re: Silicone conducting?

I guess I've not been fully understanding this. I've thought that when AC coupled, then you dont want positive DC on the grids. Im also unsure of why this design puts DC on the presence pot. I thought DC on a pot was highly undesirable.
by mrn1ngstr
Tue Apr 03, 2018 9:48 pm
Forum: Trainwreck Discussion
Topic: Silicone conducting?
Replies: 60
Views: 8031

Re: Silicone conducting?

Also, just to clarify, the only problem at this point is the crackle. Once I pulled the bus off the pots, the hum disappeared. It closest resembles the sound of crumpling a paper bag, not too hard, but steady.
by mrn1ngstr
Tue Apr 03, 2018 8:56 pm
Forum: Trainwreck Discussion
Topic: Silicone conducting?
Replies: 60
Views: 8031

Re: Silicone conducting?

I still think its got to do with the DC on the grids of the PI, but I cant for the life of me figure out where its coming from. There is supposed to be dc on the grids of a LTP PI. Look at how much voltage is on the cathode. If there was zero volts on the grids the tubes would be cut off. Sluckey, ...
by mrn1ngstr
Tue Apr 03, 2018 2:59 am
Forum: Trainwreck Discussion
Topic: Silicone conducting?
Replies: 60
Views: 8031

Re: Silicone conducting?

So I removed the bus off the back of the pots. I ran a new bus from the ground lug of the presence pot to the ground lug of the volume pot to a chassis grounded lug. The rest of the points that were tied to the original bus are still tied to it- it just no longer relying on the pot cases to reach gr...
by mrn1ngstr
Fri Mar 30, 2018 8:28 pm
Forum: Trainwreck Discussion
Topic: Silicone conducting?
Replies: 60
Views: 8031

Re: Silicone conducting?

Pdf64, do you mean you grounded the pots to the new point?
by mrn1ngstr
Fri Mar 30, 2018 7:48 pm
Forum: Trainwreck Discussion
Topic: Silicone conducting?
Replies: 60
Views: 8031

Re: Silicone conducting?

Pdf64, do you mean you grounded the pots to the new point?
by mrn1ngstr
Fri Mar 30, 2018 12:21 am
Forum: Trainwreck Discussion
Topic: Silicone conducting?
Replies: 60
Views: 8031

Re: Silicone conducting?

Yeah, I know continuity doesnt necessarily equate to grounded. I use it more to see that the path is at least there. You got me thinking though, and I just checked. .6 ohms is the most resistance I could find, from the bus to the ground lug on the IEC. Most all other ground points were showing .3-.4...