dodgy power input

[tweedgv]

HI guys,

i have recently been experiencing power cuts on the Crack.  I have swapped power cables (i'm in the UK), and the issue persists.  in order to get a constant source of power to the crack i have to wiggle the lead, putting slight pressure to pull the input back towards the outer chassis.  i have checked the wiring and it all seems as solid as the day i built it.  I guess i'm wondering if this is a common issue and an easy resolve can be sent my way.

I have recently received my speedball upgrade and would like to resolve the above issue before i start snipping away at it in its current state. 

thanks

Gav

[Doc B.]

First check the fuse to make sure it is in properly. Also check the solder joints of the wire connections to the power inlet. That would be the most likely issue. If both of those things are OK it is either an intermittent contact between the cord end and the inlet prongs, or possibly the inlet was overheated during construction and a prong is wiggling a bit. You can try moving the inlet prongs to see if this is the case. If it is, replacement of the power inlet would be the best solution.

[tweedgv]

Thank you Doc.... the response time is honestly insane.   

[tweedgv]

I'm not sure whether is should start a new thread with this but here goes.... i followed your instruction and i believe i have solved my initial problem with the power in....  i have continued with the speedball mod this evening and have fallen at the first voltage check.  i have gone through everything again and again and can't see the problem.  i have desoldered most joints but i am nervous of damaging the board so want to check the most common faults.  This is my first attempt at soldering a board since school.

The LEDs are not working.  The metre reading are all within range but none of the LEDs are working...  think i can see a slight glow from D2 but nothing like the glow from the LEDS in the original crack build. 

 

Actually... i think i can see a slight glow from all.... is it just my failing eyesight and the LEDs are a lot dimmer than the LEDs in the stock crack?

[Paul Birkeland]

What voltages do you get for the voltage checks at the first PC board?

[tweedgv]

the checks were:

OA            81.6
1A            165.8
B-A/B       0
1B            166
OB            82.3

After i posted, i convinced myself everything was ok, so i moved on.  i'm now trying to get a reading on the resistance check but am getting 0.  and i'm cursing my over eagerness to proceed without your say so.   

[Paul Birkeland]

Which resistance is 0 ohms?

[tweedgv]

OA

[Paul Birkeland]

I would recommend going back and reviewing the mounting instructions for the TIP50 on the A side and its associated hardware. 

When this resistance is 0, either the OA wire is going to the wrong terminal on the 5 lug strip at the octal socket, or the TIP50 metal tab is touching the heatsink.

Whichever situation you have, powering up the amp will cause some problems.

-PB

[tweedgv]

sorry..... when i said 0, i actually meant no reading.  the same reading as when the two probes are not touching anything.  and i'm not sure what i've done now, but both OA and OB are not giving a reading, and i haven't done anything to the B side at all. 

[Paul Birkeland]

No reading is good, 0 ohms is bad.

[tweedgv]

hahaha..... well that does sound a little more promising.   So it's good that my metre is not showing any reading at all when i probe the Ground to OB and OA???  How good are we talking Mr. Birkeland?  good enough to proceed with the voltage check?

[Paul Birkeland]

Yeah, that's a good reading, go ahead and power up.

[tweedgv]

Thanks a lot both.... i guess i was just being a little overly cautious.  haha.

The OA and OB are just a tiny bit high. 107-108.  That's fine though right?

it does sound amazing.... i expected it to, but....

[Paul Birkeland]

Yes, that's OK.