Crack Speedball hpjun's trouble shooting thread [resolved]

[Doc B.]

Are the tube pins nice and clean? Is there any damage to a capacitor?

[hpjun]

The Caps don't look damaged, it only starts to ring when I have the crack on for a long time and when I turn it off it goes away. I'll inspect the pins and clean it if it looks dirty.

I also want to know what type of 12au7 I have. It says 12au7a and has no logo on it and doesn't have any indication of a brand name it seems like its just unbranded.

I am thinking of getting a telefunken or gold lion 12au7 to test out later on.

edit: attached picture to help identify my 12au7a, also the pins look dirty going to clean them.

[hpjun]

I cleaned the 12au7a and it sounded better not sure what channged but subjectively it sounded better, it could be bias. So I went ahead and cleaned the power tube as well. I might even get some small pipe cleaners for the sockets as well. I don't have an hour at this time to listen to the ringing but when post again if hear it later on.

edit:
Ok I hear that faint ringing now and it doesn't take an hour of warm up to hear it. It sounds like it might be from the power supply area or the capacitors.

[Paul Birkeland]

I also want to know what type of 12au7 I have. It says 12au7a and has no logo on it and doesn't have any indication of a brand name it seems like its just unbranded.

That's an RCA 12AU7.

Does the amp ring when powered up with no tubes in?

[hpjun]

I just removed both tubes and powered it on and it was silent.

It's safe to do this right? the speedball board doesn't light up with no tubes in.

When I tested earlier with the tubes in I put my ear close to the 12au7 and it was the noisy one. I hear a hissing, ringing and sometimes emi noise.

I think the problem might be the 12au7 tube.

I am going to get a telefunken tube.

[hpjun]

When I tap on the big power tube the ringing noise stops and then comes back later on. yep it's the power tube not the 12au7. but once it resonates the little 12au7 picks up on it and will resonate also.

edit: taping on the 12au7 also stop it from ringing but tapping the on big one is key though.

[Deluk]

Some people find that a silicone ring or two will solve the problem but a new 6080 is inexpensive and I'd go down that route first. If you can get another 12au7 from the same vendor at the same time that won't up the bill very much and you'll save on postage.

[hpjun]

Yesterday I decided to rewire the AC heater wire to the first power tube for optimal results, (I wanted a balanced and tight winding to lower the ac hum further).

I thought I did a good job so I turned it on (my mistake for not performing resistance check). none of the boards lighted up and one of the resistors was smoking so I turned it off really quick.

I did some measurements and got infinite ohms for terminal 7 and 9.

I checked resistance between terminal 4 and 5 was at 0 ohms (one probe on 4 and other on 5). I was wondering is terminal 4 and 5 supposed to be bridged? or did I do something wrong? I know I messed with the AC heater wires so the problem is around that area.

Edit: I think terminals 7 and 9 becomes infinite ohms when speedball is installed right? What about terminal 4 to 5 when probed I got 0 ohms. I don't want to risk turning on my crack for voltage checks, last time the 270k ohm resistors got really hot and smoked the wires (good clue for what's going on) and none of the boards lighted up. Not sure how to continue the resistance checks for speedball.

[hpjun]

bump, I'd like to get help on this.

[Doc B.]

How exactly did you proceed when you rewired the AC heater wiring, meaning what wires did you disconnect and reconnect? This could be multiple issues as it sounds like you have a shorted front Speedball board and that may have happened due to a miswire of the redone heater wiring. Was the kit working with the Speedball before you redid the heater wiring?

[Paul Birkeland]

I thought I did a good job so I turned it on (my mistake for not performing resistance check). none of the boards lighted up and one of the resistors was smoking so I turned it off really quick.

This is almost always the mounting method of the TIP50C.  If improperly mounted, it could cause the problems you're describing at any given time. 

The AC wires that heat the tubes will not cause these kinds of problems unless you remove them and wire them to the incorrect location.

You'll need to carefully measure voltages for us to know what's going on.  If you have a smoking 270 Ohm resistor, you could start by measuring the voltages with just the 12AU7 installed in the amplifier and not the 6080.

[hpjun]

My wires heater wires was soldiered properly and terminal 12 got touched up a bit I also rewired the connectors from terminal 6,7 connecting to 9,10. It might be terminal 12 that has an issue. terminal 4 was grounded to terminal 12.

Is terminal 4 & 5 supposed to be bridged? I took off the ac heater wire and measured terminal 4 to terminal 5 and still at 0 ohms. I just want to be sure about this because I don't want to short the power supply. Also terminal 4 and 5 are both grounded. Also I read that terminal 4 & 5 is supposed to have a fluctating reading since it's connected to the caps, I get 0 ohms instead.

I also noticed the 6080 tube has something loose inside that is rattling when I shake it, is it a broken tube?

I am a little scared to turn on my amp for voltage checks. I am mostly worried about terminal 4 and 5 please answer that question.

[Paul Birkeland]

There are no resistance measurements in the Speedball manual for reasons like this.

When you ask about terminals 4 and 5, do you mean on the 5 lug terminal strip at the front of the chassis, or power transformer terminals 4 and 5?

[hpjun]

Yeah the power supply transformers 4&5. The ac heaters for the tubes.

[Paul Birkeland]

Yes, one end is hard grounded, and the winding itself is several turns of thick wire, so it will also read as a short to ground.