Some Minor Questions From a New Owner

[BetaC]

As these specific questions weren't in the FAQ, I thought I would create a thread for them. About two days ago I managed to score a Silver/Black TI-99/4A with a transformer, Composite Cable, ten carts and an Atari style joystick adapter for $45. It was sold as non-working, and I was able to get it all disassembled without too much of an issue. I've replaced the thermal paste on the graphics chip, and have checked for bad caps, and all seems well on that front. I was able to get the system to boot by taking the extra plug/fuse off the wall-side of the transformer, and outside of the keyboard having Mitsumi-based issues, there's nothing "wrong" with how it's working. Hell, I was able to play Parsec, sorta. As for the questions, they are as follows:

1. I can hear coil whine coming from the red-coil on the power supply board when the system is powered on. Is there anything I can do to fix that issue? I'm fine with through-hole soldering if it's necessary, and won't be afraid of changing that board entirely if needed.
2. Is it safe to run the transformer without the fuse? I haven't been running the system for long thanks to the keyboard issues, so I'm hopefully staving off damage.
3. How common is it to find a non-Mitsumi keyboard available for purchase? Would an adapter board for a modern keyboard or somewhat retro work better in the long-run? I have ADB, PS/2, AT and USB keyboards available if so.

Edited July 22, 2021 by BetaC

[+arcadeshopper]

As these specific questions weren't in the FAQ, I thought I would create a thread for them. About two days ago I managed to score a Silver/Black TI-99/4A with a transformer, Composite Cable, ten carts and an Atari style joystick adapter for $45. It was sold as non-working, and I was able to get it all disassembled without too much of an issue. I've replaced the thermal paste on the graphics chip, and have checked for bad caps, and all seems well on that front. I was able to get the system to boot by taking the extra plug/fuse off the wall-side of the transformer, and outside of the keyboard having Mitsumi-based issues, there's nothing "wrong" with how it's working. Hell, I was able to play Parsec, sorta. As for the questions, they are as follows:

1. I can hear coil whine coming from the red-coil on the power supply board when the system is powered on. Is there anything I can do to fix that issue? I'm fine with through-hole soldering if it's necessary, and won't be afraid of changing that board entirely if needed.
2. Is it safe to run the transformer without the fuse? I haven't been running the system for long thanks to the keyboard issues, so I'm hopefully staving off damage.
3. How common is it to find a non-Mitsumi keyboard available for purchase? Would an adapter board for a modern keyboard or somewhat retro work better in the long-run? I have ADB, PS/2, AT and USB keyboards available if so.

I'd just swap with a quieter ps board I have them in stock if you need

Fuse is just to prevent any kind of short from giving anyone a shock on the computer the odds of this happening are miniscule and frankly if you're using a power strip that has a circuit breaker you basically have the same thing.. plus you know the circuit breaker in your house

Good luck finding keyboard for reasonable price these days they pop up on eBay for 50 bucks or more for just the keyboard the mitsumi can be refurbished to work better..
USB and PS2 interfaces are available but they require a little bit of hardware hacking to install I sell the USB interface in my store



Sent from my LM-V600 using Tapatalk

[HOME AUTOMATION]

4 hours ago, BetaC said:

 

  2. Is it safe to run the transformer without the fuse?

 

 My understanding is that the little fuse is as much or more for fire/smoke prevention as it is for shock avoidance. It's of much lower amperage and faster acting than service panel/power strip breakers.

 

Some TI transformers run hot as is...  a prolonged over-voltage condition can supposedly cause the inner windings insulation to fail, this causes mounting hysteresis, and can lead to a thermal runaway type failure.

 

Best practice here; is to use as low an amperage rated fuse as feasible and or physically isolate the transformer from flammable conditions, while allowing generously for thermal radiation.

 

⚡???️

 

[BetaC]

2 hours ago, arcadeshopper said:

 

 

I'd just swap with a quieter ps board I have them in stock if you need

Fuse is just to prevent any kind of short from giving anyone a shock on the computer the odds of this happening are miniscule and frankly if you're using a power strip that has a circuit breaker you basically have the same thing.. plus you know the circuit breaker in your house

Good luck finding keyboard for reasonable price these days they pop up on eBay for 50 bucks or more for just the keyboard the mitsumi can be refurbished to work better..
USB and PS2 interfaces are available but they require a little bit of hardware hacking to install I sell the USB interface in my store



Sent from my LM-V600 using Tapatalk
 

 

I will keep those in mind, thanks.

 

21 minutes ago, HOME AUTOMATION said:

 My understanding is that the little fuse is as much or more for fire/smoke prevention as it is for shock avoidance. It's of much lower amperage and faster acting than service panel/power strip breakers.

 

Some TI transformers run hot as is...  a prolonged over-voltage condition can supposedly cause the inner windings insulation to fail, this causes mounting hysteresis, and can lead to a thermal runaway type failure.

 

Best practice here; is to use as low an amperage rated fuse as feasible and or physically isolate the transformer from flammable conditions, while allowing generously for thermal radiation.

 

⚡???️

 

So I shouldn't put the transformer behind my MDD G4, got it. Seriously, though, thanks.

[HOME AUTOMATION]

Although I do preach the gospel, its funny how knowing the answer... doesn't always lead to good practice...

...Mine is sitting fuse-less on the carpet.

 

     P.S. But it is on the unplug first before leaving check-list.