Speedball High Voltage on 0

[afunkymonk]

Hi All

Just running through the voltage check after installing the speedball 1.0 kit.

On the left side small board, the voltages look correct, but the right side and main board there's a high voltage reading for O. I'm on about 223v from the wall here.

Pic to follow. Any thoughts of where to start very much appreciated.

Cheers

 

[afunkymonk]

Photo here: https://scontent.fhkg3-1.fna.fbcdn.net/v/t1.0-9/87103998_3097172540327792_2765370231751704576_o.jpg?_nc_cat=100&_nc_ohc=wMse4ViRbtIAX-slL_f&_nc_ht=scontent.fhkg3-1.fna&oh=9de07cbdaae0da946cd7906d4841e008&oe=5F035654

 

[afunkymonk]

Ah - found a broken lead from R2. Will replace and check again, Sorry for wasting your time... Feel free to delete my post, mods

 

[Paul Birkeland]

Which R2? 

The issue to focus on is the high voltage coming out of the small PC board.  If you still have that issue, let us know if both socket LEDs are illuminated, or just one LED.  (The issue is very unlikely to be the LED, so do not focus on that particular part just because it's dark)

It's also worth mentioning that your kit is ancient and the LEDs can absorb moisture if they are stored in a humid environment for a long time, then that moisture can all be forced out at once during soldering, which can destroy the LED itself.  Most meters have a diode checker that will help you determine if this is an issue with your particular kit.

 

[afunkymonk]

Thanks Paul

I replaced the broken resistor - it was one of the pair at R2 on the right side of the main board.

I'm unfortunately still having voltage issues:

Board A

I = 165v
O = 105v

Board B

I - 165v
O = 159v

Main Board

B+ = 165v
O = 157v

The amp was working well before I did the speedball install. I actually made up the boards when I go the kit, but never got around to installing them. The LEDs all light, although the pair on the B board warm up slower than the A board.

 

[Paul Birkeland]

Do you have the R1 resistors in the correct spots?  One of the changes that came with Speedball 1.1 was making the R1 resistors look physically very different because people just threw them in without carefully checking them.  If both the socket LEDs illuminate and you have 159V on the output of one of the small PC boards, this is most likely a swapped R1 resistor.

 

[afunkymonk]

I metered them in situ -

R1 on A and B both measure 236 ohms

R1 on main board both read 31.6 ohms

This matches what the instructions say. Any other suggestions? Could it be a bad transistor?

 

[Paul Birkeland]

I would resolder the center leg of the MJE350 on the offending PC board (and perhaps the rest of the joints while you're in there).

Since you have the older Speedball, you also have 2N2222 and 2N2907 transistors in your kit that look identical.  Switching those by accident can also cause some problems (and we went to a PN2907 in the newer Speedball that looks different to prevent this).

 

[afunkymonk]

Hi Paul

Thanks for all your suggestions. Still no joy. I'm wondering if the best thing is just to order the small parts and start again.

 

[Paul Birkeland]

Was your Speedball 1.0 stored in a humid location in the 3+ years it has been sitting?  If so the red LEDs can absorb moisture over time and break when you go to solder them.  I have only experienced this happening for folks in humid areas who stored their LEDs for quite some time in an area without air conditioning.

 

[afunkymonk]

It is humid here, but I soldered up the boards when I first bought the kit, and all the LEDs light up when the circuit is powered up.

 

[Paul Birkeland]

It really does look like the R1 on your A board is a 31.6 ohm resistor in the photo you posted.

Since you measured them, maybe you could post a photo of the top and bottom of that particular PC board.

 

[afunkymonk]

Thanks for your patience PB - some more pics below, hopefully you spot something...


https://scontent.fhkg4-2.fna.fbcdn.net/v/t1.0-9/87153492_3105629092815470_5868784007793082368_o.jpg?_nc_cat=111&_nc_sid=a61e81&_nc_ohc=bg0lv6aKSS0AX81Giqm&_nc_ht=scontent.fhkg4-2.fna&oh=1067c94f34c2005b2a229127632649a6&oe=5EFDCC35

https://scontent.fhkg4-2.fna.fbcdn.net/v/t1.0-9/87296511_3105630476148665_8912847988708081664_o.jpg?_nc_cat=103&_nc_sid=a61e81&_nc_ohc=PldVahxXClQAX_DIy-H&_nc_ht=scontent.fhkg4-2.fna&oh=330ad28f86f23d05c73e35d5f8560e4f&oe=5EEDAA9B

https://scontent.fhkg4-2.fna.fbcdn.net/v/t1.0-9/p720x720/87788801_3105632002815179_1490372618287579136_o.jpg?_nc_cat=109&_nc_sid=a61e81&_nc_ohc=OB_xkbaWNjsAX9qD_vD&_nc_ht=scontent.fhkg4-2.fna&_nc_tp=6&oh=c0fdef3b10bc9fe7be2b74544841fb9a&oe=5EB71D05

https://scontent.fhkg4-1.fna.fbcdn.net/v/t1.0-9/p720x720/85227885_3105632932815086_5573622263095230464_o.jpg?_nc_cat=107&_nc_sid=a61e81&_nc_ohc=Qfg2xIUANuMAX9cvwnq&_nc_ht=scontent.fhkg4-1.fna&_nc_tp=6&oh=237d5a9b97110c293614742dab9f8dc3&oe=5EF666BB

 

[Paul Birkeland]

The bottoms of those boards show lots of cold joints.  Everything other than the LEDs should be reheated.  If you happen to be using lead free solder, I would grab some 60/40 leaded solder.  You should heat the joints until the solder wicks through the joint to the other side.  In particular, the center leg of each MJE350 will take a ton of heat to solder properly.