qmp audio

Re: 1176 in 51x/500 format, or 51X-F76 Build Support Thread
« Reply #220 on: July 29, 2014, 03:29:17 PM »
OK - I took a look at the data sheet and measured the holes on the PCB - these should fit.

Excellent.  Thanks for checking, that is very helpful.    Ok,  i have my entire mouser bom put together... except I am not skilled enough to now how to choose replacements for the transistors on the igor cascode amp.  I may just end up using 'original' amps,  but would like to try the cascode amps also.

the following seem to be unavailable.   What have you all been using?  will bc550 replace the 2484 if reversed?  What about a replacement for the 2SK170?
2SK170
2484


mtw

Re: 1176 in 51x/500 format, or 51X-F76 Build Support Thread
« Reply #221 on: July 29, 2014, 03:43:10 PM »
I just sent payment for 2 x 2SK170 to the fellow that runs https://sites.google.com/site/diypartsstore/catalog/transistors-diodes

As far as the 2484 goes I think this Mouser part number will work? 610-2N2484

mtw

Re: 1176 in 51x/500 format, or 51X-F76 Build Support Thread
« Reply #222 on: July 29, 2014, 04:14:06 PM »
Whoa there!

I was just re-reviewing this thread, and it looks like Taliska found that the emitter and collector on the Albatross PCB are swapped with regards to the Central Semiconductor pinout:  http://groupdiy.com/index.php?topic=43338.msg706062#msg706062

so... caveat applumbator!!

mtw

Re: 1176 in 51x/500 format, or 51X-F76 Build Support Thread
« Reply #223 on: July 05, 2015, 05:39:25 PM »
Hi All,

Wow, this is one of those projects that has dragged on for ages for me...

Anyway I'm working on getting one of my units calibrated, which I'll call unit A.

Here's what I've done:

  • got Igor's "original" input DOA set to read .8V between output and ground
  • read -9.8V on the output regulator
  • read +24v and -24v on the correct DOA socket positions
  • read correct voltages on R91, R92, R93, R94
  • pulled out the audio/gain reduction transistors and jumpered pins 9&10
  • fed a .1V RMS signal into the unit, and measured 8V :o on the output.

I'm using a JE-990 output DOA from Hairball configured to work at 24v.

While I was double checking the board, C15 and one of the 2484s on the output DOA blew out. (Loud POP from the capacitor and the 2484 is leaking some fluid.)

So... I have no idea what to do about this 8V output issue. Unit B exhibits similar behavior so I've obviously done something incorrectly on both motherboards, but I don't even know where to start looking.

Has anyone seen this behavior before? If so, did you debug it and figure out what was wrong?
« Last Edit: July 05, 2015, 07:51:58 PM by mtw »

mtw

Re: 1176 in 51x/500 format, or 51X-F76 Build Support Thread
« Reply #224 on: July 05, 2015, 06:15:13 PM »
some further debugging:

I removed the output DOA and left the input, turned input pot to max and measured the OUT terminal of the input DOA with the following (1k sine) signals (and results):

IN voltageOUT voltage
0.01V RMS0.2V RMS
0.1V RMS1.8V RMS

I then turned the output pot all the way up and measured +IN at the output amp terminal - it reads the same as the OUT terminal.

I also removed R11' (560k resistor on the underside of the mother board) - similar results.

Seems to me the problem probably lies with the 990 DOA.

Do these values seem sane?
« Last Edit: July 05, 2015, 07:00:57 PM by mtw »

Re: 1176 in 51x/500 format, or 51X-F76 Build Support Thread
« Reply #225 on: November 15, 2017, 01:41:40 AM »
Hi guys, does anyone have the documents for this build? The link in post 1 are dead.

ramshackles

Re: 1176 in 51x/500 format, or 51X-F76 Build Support Thread
« Reply #226 on: November 15, 2017, 12:12:59 PM »
Ill get them online soon

Re: 1176 in 51x/500 format, or 51X-F76 Build Support Thread
« Reply #227 on: September 12, 2019, 02:46:07 PM »
Apologies for the necro, but does anyone have the build docs for this?

TillM


Re: 1176 in 51x/500 format, or 51X-F76 Build Support Thread
« Reply #229 on: September 12, 2019, 05:10:20 PM »
Thanks


 

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