Dlite starting up problems

[Ed de Jager]

Hi All,i finally had the time to power up my Dlite this afternoon.
There is a buzz comming out of the speaker which becomes very loud when i touch the 82 K plate resistor of V3.
I attached some pictures,they are not very good but i hope they are enough.
I went over all the wiring several times before powering up and can`t find the problem.
The voltages are not too far off exept for the voltages on the plates of V3,they seem to drift.
I don`t understand what the problem is.
Can someone please help me out?
Thanks in advance,Ed

[Ed de Jager]

Sorry,i forgot:
Voltages are;V1 pin1 206,4V,pin6 215,3V.
V2 pin1 212,7V,pin 211,4V
V3 pin1 ranging fom 284-295V,pin 304,4V
V5 pin3 416V,pin4 412V.
V5 pin3 416V,pin4 413V.
Bias taps -19mV

Ed

[Normster]

It looks like you're using insulated speaker jacks (Cliff?) so you'll need to run a ground to the chassis from the black secondary connection.

[Ed de Jager]

Me again;i realize the heaters are not wired in the pictures.
They were taken before i put them in.
Heater voltages are o.k. Btw.

Ed

[Ed de Jager]

Thanks Normster,i`ll put that in.

Ed

[Funkalicousgroove]

Have you double checked your solder joints at the PI, both on the board and at the tube socket?

Are all your eyelets clean on the underside of the board? could be your bias voltage making contact through 1 strand of wire or something like that.

Are you using new tube sockets or a Donor chassis?

If it is a donor chassis you should re-tension the tube sockets with a dental tool (They sell them at Walmart among other places).

[Ed de Jager]

I have put in the ground connection and the noise is gone exept for the PI issue.
When i touch the 0.o22uF cap going from the 82k to the 220k resistors i get strange oxillation like noises.
Both sides of the cap.
Does that sound like a bad cap?i checked the solderconnections.
I will reflow them first.
Too bad i am out of sparetime for today.I hope i will have some time tommorrow.
Thanks for te suggestions!

Ed

[ampgeek]

Hey Ed,

Do you get anything "musical" out of it when you plug your guitar in and play?

Just wondering what the extent of the problem really is.
Dave O.

[Normster]

Please post a clear photo of the PI section including the tube socket connections. It may give us a clue of what were looking for. Another area that can cause problems is the presence pot ground. (Yet another photo would be helpful.) Also, don't discount a bad tube as the cause. Maybe swap V2 and V3.

[Ed de Jager]

Ampgeek.i didn`t plug my guitar in yet;wanted to get rid of the problems first.
Normster,i will put up the pictures you asked for tomorrow.
Thanks for the help,it is greatly appreciated!

Ed

[Ed de Jager]

I hope these pictures will clear things up.

Ed

[Ed de Jager]

Hi,with all this debugging i completely forgot to plug a guitar in the amp.
Everything works,i had to stop within 5 minutes because my kids were watching T.V.and everything but i have to say i liked what i was hearing.
It still is a little noisy but i expect that that is due to the PI thing.
I hope someone comes up with a suggestion through the new pictures i posted.
All in all a big THANK YOU to Normster who made this all possible!!

Greetings,Ed

[drz400]

I have put in the ground connection and the noise is gone exept for the PI issue.
When i touch the 0.o22uF cap going from the 82k to the 220k resistors i get strange oxillation like noises.
Both sides of the cap.
Does that sound like a bad cap?i checked the solderconnections.
I will reflow them first.
Too bad i am out of sparetime for today.I hope i will have some time tommorrow.
Thanks for te suggestions!

Ed

You shouldnt be touching coupling caps, touch the wrong side and you will get zapped! If it sounds good you are fine, if you really want to know try and look at it on a scope. Dont judge the circuit is faulty because you touch a part and it makes noise though!

[Ed de Jager]

Thanks for the concern but i touched it with the probe of my meter.
It is connected to the 82K plate resistor.

Ed

[ampgeek]

Whew...I was beginning to worry that you would never get to the most important "test" because you were chasing non-issues. DRZ has already provided that excellent advice.

FWIW: there aren't many places in an amp that don't cause some kind of "noise" (either intermittent or sustained) when probed with a meter. Pops, hisses, buzzing, yaddaa...yaddaa...are definetly not out of the ordinary when probing around with a DVM. I think that I still have a couple of pair of permanently stained shorts from the frightening "pop" caused by probing the power tube plates with the volume full up!

What you are describing is similar to something that I experienced recently. Turned out that it was "noise" from my overhead fluourescent lights "leaking" into the LV section(s) of my PI when I clamped on the leads. The leads were acting like a big old antenna. Similar effects come from AC motors (freezers, refrigerators, water pumps, etc...). So...check around for those types of noise sources.

Also, double check your shielded wire sections against the layout. Make sure that only one side of the shield is grounded. Triple check your overall grounding system as well.

Sounds like you are really close though.
Good luck!
Dave O.