Phantom drive?
in [Commodore]
|
Prev: Starcraft for C64
Next: Breadbox vs C64c - reliability?
From: Martin 'Martinland' Schemitsch on 5 Nov 2009 16:47 On Thu, 05 Nov 2009 12:28:34 +0100, Paul F�rster <paul.foerster(a)gmx.net> wrote: > Hi, > On 2009-11-05 12:04:46 +0100, Paul F�rster <paul.foerster(a)gmx.net> said: >> I already checked CIA2, U21, U22 and U23 and replaced them with known >> good parts. The symptom remains. > ... oops! That was meant to be CIA2, U21, U22 and U3, not U23. Sorry. What about U2, they make good music too! OK, I tried, sorry... ;) ML -- ---------------------------------------------------------- "I don't know. I'm making this up as I go!" (Ford as Dr. Jones Jr. in 'Raiders of the Lost Ark') ----------------------------------------------------------
From: Paul Förster on 6 Nov 2009 02:19 Hi Martin, On 2009-11-05 22:47:37 +0100, "Martin 'Martinland' Schemitsch" <team8martinland(a)hotmail.com> said: > What about U2, they make good music too! > OK, I tried, sorry... ;) .... that's a matter of taste. But CIA2 sits in position U2. So unfortunately, it doesn't help me. -- cul8er Paul paul.foerster(a)gmx.net
From: Ruud on 6 Nov 2009 07:22 Hallo Paul, > ... I already checked a couple of times. And I've tried three different > 7406 chips, to no avail. That's why I ask. I meant that you have to check if there is a short circuit between Data and Ground and/or Clock and Ground. Preferably with no 7406 in the socket. Just an idea: what you can do is insert CIA2 but leave out all pins involved with the IEC bus. IMHO in this way the C64 should act as if there is no drive connected. -- ___ / __|__ / / |_/ Groetjes, Ruud \ \__|_\ \___| http://Ruud.C64.org
From: Paul Förster on 6 Nov 2009 10:16 Hi Ruud, On 2009-11-06 13:22:22 +0100, Ruud <Ruud.Baltissen(a)apg.nl> said: > I meant that you have to check if there is a short circuit between > Data and Ground and/or Clock and Ground. Preferably with no 7406 in > the socket. .... I tried without the 7406. If I do that, the screen stays blank when powering on... I'll cross-check the lines again. Maybe I missed something. > Just an idea: what you can do is insert CIA2 but leave out all pins > involved with the IEC bus. IMHO in this way the C64 should act as if > there is no drive connected. .... according to the schematics, that would be pins 5 (ATN OUT), 6 (CLK OUT), 7 (DATA OUT) and 9 (DATA) of CIA2, right? Pin 8 (CLK) has a connection to pin 4 of U22, but what would happen to the CIA if it was inserted without a clock signal? Would that damage the CIA? Also, pin 24 (FLAG) of CIA1 is connected to the serial port. But the latter goes to CASS RD (D, 4) on the cassette port too and cassette works fine. So I wouldn't suspect the problem there. And there are definitely no shorts between each of the serial bus connections. I checked all possible combinations. Ok, I'll prepare a socket for the CIA2 test. I don't want to bend the CIA chip's pins. CIAs are too precious chips. Also, I try them in sequence and not all at once. That'd give me more information about which one might be the culprit. I'll keep you posted. Thanks very much for helping. :-) I hope I can locate the problem. -- cul8er Paul paul.foerster(a)gmx.net
From: Paul Förster on 6 Nov 2009 10:41
Hi Ruud, .... ok, here's an update: On 2009-11-06 13:22:22 +0100, Ruud <Ruud.Baltissen(a)apg.nl> said: > I meant that you have to check if there is a short circuit between > Data and Ground and/or Clock and Ground. Preferably with no 7406 in > the socket. .... oh, this is strange. The C64 wouldn't show a picture without the 7406 previously. Now it does. Don't aks me why... You made me curious to give it another shot and so I removed the 7406 again and now the C64 properly powers on. I've cross-checked all combinations, not just neighboring lines of the serial connector and the 7406 socket each. There are no other shorts than pin 1 and pin 5 of the 7406, which according to the schematics is correct. Anyway, having removed the 7406 and powered on the C64, it correctly shows DEVICE NOT PRESENT. So my guess is the chip is bad. But that wouldn't explain why 6 brand new chips fresh from the factory don't work. BUT: I have ordered a brand new load of 7406 chips and tried 6 of them. All with the same result. I cannot imagine that 60% of the brand new load should be defective... The old chip reads: 7406N FDY5150 8741VJ The new chips read: 84H5RCK E4 <- the "E4" is small printed and underlined SN7406N The former (old) chip has a big "S" printed in front of it. Is that the manufacturer? And if so, what is it? The new chips are made by TI. They bear the Texas Instruments logo. Is there any difference between these chips? Have I tried the wrong chips? Maybe I try and desolder the one of the dead board you gave me (which I have butchered halfway anyway ;-) and try that chip... -- cul8er Paul paul.foerster(a)gmx.net |