Twentieth Anniversary Macintosh rehabbing

[Njb796]

So I am working on a special project...
Long post... TLDR basics are in bold.

I got my hands on a TAM this week. It's definitely a well used unit. I did the work of replacing the audio connectors and tinning the connections on the board in the base unit/subwoofer to preempt the famous bose buzzing. The unit came to me as not booting up - no screen displaying. I have yet to determine what that's about. I tried the reset PRAM keyboard combo to see if it would chime again, (which would help me determine if it was the screen that went bad or something else) but it did not chime again so I dont think it is the display. Probably a recapping is in my future.

That being said, I did notice something rather odd and I can't seem to find any guidance online for this. When I power up, the front speakers make a hissing, like a loud fan or static. It is not coming from the subwoofer. It's immediately when I turn it on. On a hunch, I left the base unit/subwoofer open since I was test booting after the tinning and new audio connectors. When I disconnect the two wire connector that goes from the logic board in the base to the subwoofer, the front speakers still make the sound. When I disconnect the umbilical from the board in the base, the unit powers up... does not make a chime, and there is no hissing.

Any thoughts? I did read on here replacing the PRAM battery may help with the booting. But that hissing is so loud... like a loud fan. Any ideas?
A couple other things on my list... I redid the keyboard using a PowerBook 3400 keyboard that was in like-new condition. Gave me a chance to really clean up the trackpad. But I also need to recover the speakers - the cloth on there has some coffee stain on it that won't come out. The previous user must have also used a lot of wrist jewelry because the leather wrist rest is all jacked. So I want to recover the wrist rest with new leather. Any recommendations from anyone else who has done either of these things?

Also - I am a total amateur who thinks he can recap. I can't. Any recommendations on who might do recapping if I send them the boards?

 

[bibilit]

I have not worked on a TAM often, but capacitors are not always the magic solution.

Are you sure you are getting all voltages required from the power supply ?

Try removing any card present (if you have) remove the HD and try booting with a basic setup. If no improvement you can have a look at capacitors, but the TAM is not easy to work on, with brittle plastic and tight space.

The battery is not required to get a boot.

 

[Byrd]

Hi njb796,

Congrats on finding a TAM, I also had a well used one that came up well with some restoration time. You will find posts on here about recapping the unit (and subwoofer/PSU), personally I'm yet to tackle mine as there is no evidence of leaking but imagine I'll have to do it in a few years' time. But - if you run a cotton tip around the motherboard caps and get a greasy/oily residue it is time to undertake.

Did your unit only chime once with no display? Often the displays fail due to bad backlighting or get into a dead state due to some sort of PRAM/CUDA issue, leaving it unplugged for a day, not plugged in no backup battery and pressing the CUDA switch can bring it back to booting. Also the usual change RAM, check all connectors.

The speakers are quite unique and I'm yet to find an off the shelf replacement; the fact that yours screech is not a good sign suggesting some sort of hardware failure. Did you re-tin the umbilical cord and find this happen after - and why did you do this before doing other troubleshooting? "Speaker buzz" is a common fault but the TAM still works fine without it being rectified.

Confirming that the speaker cover fabric can be replaced easily enough - head to a fabric store to find a match, and the palm rests also can be removed from the underside, leather peeled off and replaced with new pieces adhered with contact adhesive.

 

[Njb796]

Thanks @bibilit and @Byrd .

I thought it might be the display, which is why my test of holding down option+Apple+R+P would help me to some degree... I figured if it chimed again while holding down the keys, then yes, it was the screen. But seeing that it did not chime again I am figuring the problem is likely something else. It looked like there was decades of dust in there so I disassembled and blew out all of the dust cleaning it up.

@Byrd It did only chime once when I did the PRAM reset. I held it for like 2 mins... no second chime. I will take the RAM out (battery is out and unit has been unplugged). And I should add the speaker buzz isn't really a buzz... it's from the speakers on the unit, not the base, and its a loud SSSHHHHHing. I did the tinning and connectors just as a preventative measure since I had opened the base unit to clean it out. I only tinned the silver prongs on the board (where speaker wires connect and where umbilical cord plugs into board) - I didn't do anything with the cable itself. I will also try the CUDA switch (I think that's what that little grey button is). As much as I hate to say this, I dont remember it making this whisssshhhing noise when I booted it before I took apart the base unit. I went back and looked at the camera from when I turned it on before opening the base... it did NOT make the noise. Ugh. When I try moving the cables around while on, it does not alleviate the noise. Not telling what I must have done. Again - I dont think it is the connectors for the subwoofer - I still hear it which those unplugged. I have a sinking feeling in my gut.

I am on the hunt for the right fabric and leather to replace.

@bibilit Again, take this from someone who probably is undertaking a project he is not totally prepared for... How would I test the voltage from the PSU? And how would I know if those values are right? I do have an ohm meter/tester but no idea where to start.

 

[bibilit]

If you had a chime, probably the voltages are ok.

So looking for any hardware issue is a good starting point (bad Ram…)

 

[Byrd]

@Njb796 I'm sure all is not lost the TAM is a fairly reliable Mac - yes, there I said it! With some care I'd like to think you will get it up and running again. I have put my TAM in a funk where it chimes and doesn't get any further this was usually related to a marginal PRAM battery and hardware install (eg. put in G3 but didn't reset the CUDA).

The speakers - if they're both doing the same noise, it's a connection somewhere. Reseat everything with a good spray of electronic solvent cleaner, and check the tinning for marginal contacts.

Note you can boot with one single stick of RAM, all the dust check the slots and also repasting the little cheap CPU heatsink wouldn't go astray.

Where are you located? Perhaps there might be a TAM owner in your town to compare and troubleshoot.

 

[joshc]

The TAM is a machine held together with tape and crappy connectors. If you've ever opened one you'll be surprised the thing works at all. Apple engineers were smoking some special stuff when they designed this. Added to the mix is loads of electrolytic caps that are due for replacement now. The PSU is some sort of 9500-style unit if my memory serves me right.

Advice above is good but I think if I was expecting a TAM to be fully working I'd also expect to need to replace the capacitors by this point.

 

[bibilit]

The TAM is a PowerMac 6500 in a different case and with a PowerBook (3400) screen and keyboard. The PSU is a PowerMac unit or close to.