ADA Depot - A Forum To Support Users of ADA Amplification Gear

Let's Get Technical => Troubleshooting Problems => Topic started by: t-rack on November 23, 2014, 07:03:37 PM

Title: No lights No sound and a hot ic
Post by: t-rack on November 23, 2014, 07:03:37 PM: just like the title says u13 is burning hot after a couple seconds and no lights unless i start pulling out KH then they flicker. tested VR1,2,3,4 all OK. any ideas are greatly appreciated.
Title: Re: No lights No sound and a hot ic
Post by: rnolan on November 24, 2014, 04:04:23 AM: Hey t-rack MP1/2 ??
Title: Re: No lights No sound and a hot ic
Post by: MarshallJMP on November 24, 2014, 11:30:58 AM: "pulling out KH" ? what do you mean by that?

What happends if you pull U13 out ?
Title: Re: No lights No sound and a hot ic
Post by: t-rack on November 26, 2014, 02:27:17 AM: it's an MP-1 . and i believe KH is what the ribbon cable is labelled in the layout.
Title: Re: No lights No sound and a hot ic
Post by: MarshallJMP on November 26, 2014, 03:01:13 PM: Ah okay KH,the grey ribbon cable right?Now if you pull it out it won't start up because the midi board gives out interupt signals to the Z80 processor.Have tried pulling U13?
Title: Re: No lights No sound and a hot ic
Post by: t-rack on November 26, 2014, 10:41:07 PM: yes pulled u13, now u14 is hot and still no lights. like something is drawing too much current through the chips, but what?
Title: Re: No lights No sound and a hot ic
Post by: MarshallJMP on November 27, 2014, 12:21:20 PM: Are you sure your voltages are okay?measure between pin 1 and pin 7,there you should have -15V and between pin 7 and pin 16 you should have +15V.Try to pull them both out and see if it starts.
Title: Re: No lights No sound and a hot ic
Post by: t-rack on November 30, 2014, 10:01:05 AM: yes between 1 & 7 is -15v between 7&16 is 14.8v
Title: Re: No lights No sound and a hot ic
Post by: t-rack on November 30, 2014, 10:58:34 AM: Ok now i feel stupid, i am just noticing that U13,14 are the wrong IC"s . found this out comparing it to a working mp-1 i have here. correct ones are now in place but still no lights/sound except for a little flickering when i turn it on after a while. and just so you know i bought it used from someone who was "from what it looks like" trying to do the factory updates such as changing the diodes putting the jumper on U29 ect.
Title: Re: No lights No sound and a hot ic
Post by: rnolan on December 01, 2014, 03:56:42 AM: Hey t-rack, then would seem to be either something damaged with wrong chips (let MJMP know what they are hopefully he will know if that is/was a possibility) or, to me more likely (based partly on my Mate MikeBs recent experiences with the noise mod, broke a track, fiddly, suits those who do it regularly LOL), there are some issues with the previous owners attempted changes ? Mmm diodes, they tend to stop things if they're not right. May just need a re-flow/check around those components ? Anyway, hope it's that simple.
Title: Re: No lights No sound and a hot ic
Post by: MarshallJMP on December 01, 2014, 01:33:04 PM: Has pin 17 of U29 (Z80) 5V?
Title: Re: No lights No sound and a hot ic
Post by: t-rack on December 02, 2014, 05:58:27 PM: no only 1.8v
Title: Re: No lights No sound and a hot ic
Post by: MarshallJMP on December 03, 2014, 05:31:30 AM: This has to be 5V,this the NMI (non maskable interupt) input which has to be high (5V) else it will execute an interupt.So check the jumper to the 5V.
Also check R251 and check if they did the update correctly.
Title: Re: No lights No sound and a hot ic
Post by: t-rack on December 18, 2014, 05:14:50 PM: U25 has jumper from pin 17 to 24 and trace cuton pin 17. r251 removed 3.3k between u40 pin 11 u44 pin12
Title: Re: No lights No sound and a hot ic
Post by: t-rack on December 18, 2014, 05:19:34 PM: and still only 1.5vdc on pin 17
Title: Re: No lights No sound and a hot ic
Post by: MarshallJMP on December 20, 2014, 06:27:13 AM: Quote from: t-rack on December 18, 2014, 05:14:50 PM
U25 has jumper from pin 17 to 24 and trace cuton pin 17. r251 removed 3.3k between u40 pin 11 u44 pin12

Do you mean U29???

Whay voltage do you have on pin 24?
Title: Re: No lights No sound and a hot ic
Post by: t-rack on December 26, 2014, 10:26:16 PM: went over some shoddy solder joints, now have 2.5vdc at pin 17 and 24

yes u29 sorry
Title: Re: No lights No sound and a hot ic
Post by: t-rack on January 07, 2015, 07:49:50 PM: still no display or sound
Title: Re: No lights No sound and a hot ic
Post by: MarshallJMP on January 09, 2015, 12:36:21 PM: Sorry,missed your reply.Anyway 2.5V is waaaay to low,you should have 5V on pin 17,11,24 and 25.Also check the voltage on pin 28 and 26 of the eprom,is this 5V or also 2.5V?
Title: Re: No lights No sound and a hot ic
Post by: t-rack on April 28, 2015, 02:15:02 AM: i know its been a while but im back at it now, 2.5v on pins 26 and 28
Title: Re: No lights No sound and a hot ic
Post by: MarshallJMP on April 28, 2015, 02:38:42 AM: Ok measure the voltage comming out of the voltage regulator VR4,between pin 2 and 3.Should be 5V.