Search found 108 matches

by dizzy33
Sun May 31, 2020 2:12 pm
Forum: Hardware
Topic: ZX Spectrum + : no boot
Replies: 32
Views: 3588

Re: ZX Spectrum + : no boot

Hello Mark, just to confirm that the culprit for the sound was diode D9. Now the sound works fine. So in the end, this Spectrum had all these parts as bad on the motherboard : - caps (bad video quality). - ROM (dead, burning hot). - one RAM chip - D9 All I need to do now is to fix the keyboard, I ha...
by dizzy33
Wed May 13, 2020 6:40 pm
Forum: Hardware
Topic: ZX Spectrums problems : diagnostic software ?
Replies: 123
Views: 31803

Re: ZX Spectrums problems : diagnostic software ?

Thanks a lot Mark. In fact I tried a CMOS on a Spectrum with issue 4S and 6A motherboard, it works fine. I only had problems with my issue 2 motherboard. I will check the R1 to R8 value for 4S and 6A, may be I can try the same value for issue 2 ? Or may be I will just give up, thinking that I alread...
by dizzy33
Wed May 13, 2020 2:04 pm
Forum: Hardware
Topic: ZX Spectrum + : no boot
Replies: 32
Views: 3588

Re: ZX Spectrum + : no boot

Thanks a lot Mark, I have ordered some new diodes. In the mean time, I had a working Spectrum which also had a new sound problem : no sound ! So I used all your recommandations from this thread and could then find the culprit : a bad speaker. So I also need to buy a new 40 ohm speaker ... So again, ...
by dizzy33
Wed May 13, 2020 2:02 pm
Forum: Hardware
Topic: ZX Spectrums problems : diagnostic software ?
Replies: 123
Views: 31803

Re: ZX Spectrums problems : diagnostic software ?

Mark, when you say "The solution is to fit higher value resistors in positions R1 to R8", which value would you then recommand for R1 to R8 ?
I would like to be able to put any Z80 on this "issue 2" motherboard ...
Thanks again !
by dizzy33
Mon May 11, 2020 10:32 pm
Forum: Hardware
Topic: ZX Spectrums problems : diagnostic software ?
Replies: 123
Views: 31803

Re: ZX Spectrums problems : diagnostic software ?

YEEEEEEEEESSSSSSSSSSSS !!!! Another Spectrum alive !!!!! But I'm not totally satisfied ... Here is he situation : this Spectrum was displaying some graphical bugs on the very left side of the screen, and the Smartcard was sometimes showing some lower RAM chips as failed (never the same one, and thes...
by dizzy33
Mon May 11, 2020 9:06 pm
Forum: Hardware
Topic: ZX Spectrums problems : diagnostic software ?
Replies: 123
Views: 31803

Re: ZX Spectrums problems : diagnostic software ?

I replaced all the lower RAM capacitors, it did not solve the problem.
Marc, any idea of what I could try now ?
by dizzy33
Mon May 11, 2020 4:14 pm
Forum: Hardware
Topic: ZX Spectrum + : no boot
Replies: 32
Views: 3588

Re: ZX Spectrum + : no boot

Hello Mark, here is me real result (my sound tests worked better with a working ROM ...). The sound is working perfectly on my headset connected to the "EAR" connector of the Spectrum, but no sound on the speaker. I connected my oscilloscope to the anode of D9, I see a signal. But on the cathode, no...
by dizzy33
Sun May 10, 2020 11:54 pm
Forum: Hardware
Topic: ZX Spectrum + : no boot
Replies: 32
Views: 3588

Re: ZX Spectrum + : no boot

Thanks a lot Mark, but I should receive my 28 pins socket very soon (Monday or Tuesday), then I will be able to use the ROM of another Spectrum.
I will then re-do all the tests you suggested. I will let you know of the result.
by dizzy33
Sun May 10, 2020 9:59 am
Forum: Hardware
Topic: ZX Spectrum + : no boot
Replies: 32
Views: 3588

Re: ZX Spectrum + : no boot

I tested the continuity between pin 28 of ULA and D9, the continuity is OK. But that's very difficult for the moment to do these tests as my only way to let the Spectrum produces sounds is via the Smartcard, which only beep once every minute ... I have no working ROM on my motherboard so I cannot tr...
by dizzy33
Sat May 09, 2020 8:09 pm
Forum: Hardware
Topic: ZX Spectrum + : no boot
Replies: 32
Views: 3588

Re: ZX Spectrum + : no boot

Here is the result : - if I connect a headset to the "mic" connector, then I can ear the Spectrum sound. - if I connect a sound source to the "ear" connector, then I don't ear nothing from the speaker. So I connected my oscilloscope to the anode then cathode of D9 (while playing music to the ear con...