xrbrevin Posted June 27, 2018 Share Posted June 27, 2018 Hi, I hope someone can assist, i have a shabby 130xe that is reliable but it has no sound out of the monitor socket (just thought: i will have to try the RF modulator..) anyhoo, heres what ive done so far: desoldered pokey - it works fine in my 600xl desoldered LM358 (U1) - also works fine in my 600xl. metered up all the associated resistors (as specified in sams computerfacts) - R3 showed no reading. great! - or so i thought. i replaced it but sadly no change... desoldered 2x electrolytic caps to isolate out the SIO audio in: C22 C18 - still no audio so i put them back in. confirmed continuity between LM358 (U1) and modulator left pin, associated resistors: R8 R10 etc and monitor port audio pin - all ok I get a voltage from pin 37 of the pokey and there is continuity from here to capacitor C17 im wondering if an electrolytic cap is bad.. will check modulator audio now and report back ..no audio via modulator :/ Quote Link to comment Share on other sites More sharing options...
xrbrevin Posted June 28, 2018 Author Share Posted June 28, 2018 ive ordered the 4x radial electrolytic caps, if it doesnt work then i'll donate guts from this board to a 65xe board to make it 128k and keep the rest for spares make or break Quote Link to comment Share on other sites More sharing options...
+Nezgar Posted June 28, 2018 Share Posted June 28, 2018 No luck with RF audio out? Quote Link to comment Share on other sites More sharing options...
xrbrevin Posted June 28, 2018 Author Share Posted June 28, 2018 sadly not... Quote Link to comment Share on other sites More sharing options...
xrbrevin Posted June 30, 2018 Author Share Posted June 30, 2018 fitted 1x of the caps (C50) but still no sound however, i spotted an anomaly - 3x resistors are blue: see image (ignore the one on the left, i fitted this the other day). i metered them up and they are all 75ohm! (someone's been meddling....) they should be: R53: 100ohm R204: 47ohm R202: 180ohm so there is a possible solution - ive ordered new ones. fingers crossed!! Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted June 30, 2018 Share Posted June 30, 2018 fitted 1x of the caps (C50) but still no sound however, i spotted an anomaly - 3x resistors are blue: see image (ignore the one on the left, i fitted this the other day). i metered them up and they are all 75ohm! (someone's been meddling....) they should be: R53: 100ohm R204: 47ohm R202: 180ohm so there is a possible solution - ive ordered new ones. fingers crossed!! Did you look at a schematic to see what those resistors are for? I'm not super-familiar with the internals of the 130XE, but that seems like an awful specific set of changes from stock, so I've got to wonder why someone changed them. From a quick review of the 130XE SAM'S COMPUTERFACTS on AtariMania, those are all video circuit components. Unless one of them is shorting a nearby audio component or audio trace, changing them will have nothing to do with your audio issue. Rather, I'd suggest you get hold of a schematic and start tracing audio lines from POKEY to the monitor jack until you find the problem. Page 10 of the SAM'S COMPUTERFACTS has details for audio output troubleshooting. Quote Link to comment Share on other sites More sharing options...
xrbrevin Posted June 30, 2018 Author Share Posted June 30, 2018 cheers for the advice. im also intrigued to know why someone may have changed these resistors. I'll research their purposes to get an idea. im using sams computerfacts but im struggling for a keyboard to input the basic audio command! the one i have has intermittent mylar issues so unfortunately ive not been able to follow the guidance to the letter. i have traced the signal from POKEY pin 37 and the associated components are within their ratings - 1 resistor (R3) gave no rating so i replaced this (the blue one on the left in the image). i ought to re-check just to verify the results tho. i think i should get a logic probe really, its worth having one anyway Quote Link to comment Share on other sites More sharing options...
xrbrevin Posted June 30, 2018 Author Share Posted June 30, 2018 (edited) hang on, i think it might be an ultravideo xe mod... it is, oh well.. i'll leave it in back to the drawing board Edited June 30, 2018 by xrbrevin Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted June 30, 2018 Share Posted June 30, 2018 That cap to GND in front of R53 and R204 looks mangled. I don't think it's part of the audio circuit though. Worth checking for a dead short to GND on one of the audio caps. 1 Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted June 30, 2018 Share Posted June 30, 2018 That cap to GND in front of R53 and R204 looks mangled. I don't think it's part of the audio circuit though. Worth checking for a dead short to GND on one of the audio caps. yep and make sure cap cases aren't touching legs of components they are partially covering as well... Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted June 30, 2018 Share Posted June 30, 2018 Might be worth temporarily disconnecting pin 5 of the modulator as well in order to completely eliminate it as a possible issue. Quote Link to comment Share on other sites More sharing options...
xrbrevin Posted July 7, 2018 Author Share Posted July 7, 2018 fitted the 3x non-polarised electrolytic caps and no joy... decided to compare voltages with my 65xe and found that C17 (the first cap after the pokey sound output) had 2v more on the left side. swapped the cap - also no joy (killed the cap putting it back in the 65xe! gah!) decided to compare resistor readings in situ with the 65xe. R11 didnt read up as 2.2k on either board (obviously some draw from neighbouring component(s)) but they also didnt match!. i rooted around and found a new one - fitted it and instant proper sound on the 130xe!! Jackpot - its not a spare part any more of note: the removed R11 reads nothing and it has no visible damage. cheeky little beggar... many thanks again for your assistance! 1 Quote Link to comment Share on other sites More sharing options...
Like us on Facebook
Follow us on Twitter
AtariAge on Instagram
Watch us on YouTube
Chat on Discord
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.