C64 not loading from tape

BGOllie wrote: »

I was wondering about that so I went back to the schematics and interestingly it looks like the PSU sends two 9v AC lines (pins 7 and 6) to (after going to various coils and cap) 7812 and 7805 that regulate the +12 and +5v DC power. It also derives the unregulated 9v DC from this too.
But back on the psu there's another pin, going to a separate conversion that generates the 5v to keep the "Pull high" threshold for some of the chips, like the RAMS and the CIA chips. It does this via transformer and caps. So if the value is wrong coming out of the PSU some of these chips might be thrown off and not work properly.
Wouldn't hurt to check the voltages right at the PSU:

OK - I got measurements as follows:

• Pins 2 and 6 -> 9.3VAC
• Pins 2 and 7 -> 12.3VAC
• Pins 2 and 5 -> 5.02 V DC

BGOllie wrote: »

mm pin 7 should be around 9v ideally. but since it goes to a 7805 regulator then it's converted to 5v regardless. If this part failed you'd have no 5v to supply all ICs and the computer wouldn't even start. so I'd say your ok with the power supply. Pin 5 is only the one that could affect the CIA chip in the way you're experiencing and it's fine at 5.02.

One thing you could try is test the voltage across pin 1 (ground) and pin 24. It should be high (around +5v) when the tape player is off and pulled low (around 0v) when the tape is loading. This pin is an input pin, meaning the signal comes from somewhere else , in this case the tape port. So check it's high when nothing's going on, load a tape and check again :
If it is low but the tape isn't loading you most likely have an issue with the CIA chip at U1 and it needs to be replaced.
If it is high and the tape doesn't load it could mean that the tape player itself isn't sending the read signal and need to be fixed (or replaced)

Thanks for the advice Ollie - I really need to study electronics and get up to speed!!

I'll check that today hopefully - I'll double check my pin readings again too while I'm at it.

Fingers crossed it's a deck issue as opposed to a mainboard issue.

That being said I suppose I could get a new CIA chip if I really needed and put it in

Stoner wrote: »

I think I have a spare tape deck for a C64 if you are badly stuck

Thanks - I really appreciate that !! I may take you up on it, but I still need to test the stuff @BGOllie suggested first.

Actually - looking at this is seems like U2 is the one that deals with user ports ?

U1 	906108-02 (6526/ A or 8521) CIA 
     Startup screen normal but no cursor, or blank screen if chip is shorted 
(remove to test). No keyboard or joyport access. Partial failure: some keys or 
joystick positions don't work, "stuck" line may print a character at startup. 
Cartridge works.

U2 	906108-02 (6526/ A or 8521) CIA 
     Lines or blocks instead of startup screen, but blank screen if chip is 
shorted (remove to test). Partial failure: marginal or no serial / user port 
access, keyboard and cartridges still work.

Me confusted

Edit: BTW - I'm on a C64C with the "short" board - PCB ASSY No. 250469
Another Edit: Actually, I see it's pin 24 on U1 on that diagram that gets the data...

BGOllie wrote: »

you can do a continuity test just to be sure which chip is which

but the signal shifts as expected to low and the game isn't loading. Which would point to U1 being faulty indeed.
It could also be sth wrong further down the line on the Data bus, but these CIA chips are known to fail easily . I would consider changing that first.

I might still be worth checking there's activity on the other lines (ie, the data line might be having issues and not be receiving the data from the tape ) on the cassette port but you'll really need a scope or at least a logic analyser for this. Might be worth double checking with a known working tape deck first just to completely rule that part out

Yep - I'm gonna have to get my hands on a tape deck, or give mine to someone with a C64 - thanks man - you're more than just an ace musician

Dr Bob wrote: »

Hey ! I might have a spare tape drive you can borrow (that was me on reddit) . based in maynooth if its any use to you.

I could collect it next week as I pass by Maynooth on the M4 on my way to and from work.
Would that work for you ?

Dr Bob wrote: »

should be grand . let me dig it up first and then ill sort out details.

Deadly - thanks.

BTW @Stoner - I really appreciate your offer also, but Maynooth is lot handier for me as opposed to Dublin 7, but just want to say I really appreciate your offer of a deck also if I need one

So after discovering the problem is with my tape drive I went back at it.

I cleaned the heads a lot more with WD40 Contact Cleaner (It specifically says it can be used for tape heads) and I visually aligned the head as I can't run a program to do so initially.

I managed to get it to read something (Stuff like - "FOUND xCa" etc)
I played around with the alignment and eventually go it to read "COMMANDO" ( the tape I was loading) but it didn't get far past the "FOUND" part....

I then re-entered the alignment program and it makes the screen flash a bit and a few times, for a split second, I could see that dots you are supposed to use to align, but they are all over the place (not in rows)
I'll keep fiddling with it, but I suspect the head is not good.

Someone over on Lemon64 suggested it could be magnetised.

I'm reluctant to spend money on a demagnetiser as there's no guarantee that's the issue.

I'm currently looking at videos on how to make one - but I'll need a 12VAC (or around 12V) power adapter which I'm not sure I have (lots of regular DC adapters, no AC)

I don't suppose anybody round here has one they can lend me ??

BTW - here's the head, which I think looks as clean as I'll get it:

eddhorse wrote: »

My take on this is that your time is worth money, how much does another tape deck cost?

Yeah - I hear you.

Apparently there's a deguasser in work and I might be able to use it. I'm looking into it.
At this point it's pointless as I've ordered an SD2IEC anyhow.

That being said, I just want to make it work as it was MY tape drive back in the day - does that make any sense ?

Tom Mann Centuria wrote: »

Is the c64 affected by the chutney field? Worth considering.

The what now ?

Tom Mann Centuria wrote: »

Or chuntey field.

https://www.google.com/amp/s/www.urbandictionary.com/define.php%3fterm=chuntey&amp=true

LOL - I hadn't heard that one before