exxos's Atari, Amiga & retro forum

Tomswork wrote: 27 Apr 2023 09:10 I will take some

Tom

Cool :)

Don't feel you need to take it apart though.

Well, the FreDH boards are in the UK and left East Midlands airport at 0612 this morning :)

Looks like the stated delivery of Tuesday is going to be good :)

:dualthumbup:

stephen_usher wrote: 29 Apr 2023 09:54 :dualthumbup:

Since posting earlier, it's arrived in Ipswich :)

That's the delivery depot so looking good.

Well, the TRS-80 didn't power up after my cable work yesterday, so I had a closer look at the PSU, and none of the necessary voltages, so 15-17 VAC and 19-21VDC.

I popped the bottom of the PSU case off, which is held on by 4 screws and found a mass of plastic/cardboard insulation:


And buzzing out the mains input, I found there was no continuity on neutral, so opened the plug up and found the neutral connection had come adrift, so fixed that, but despite that, I still had no power at the lead that plugs into the TRS-80.

At that point I realised I needed to pull the plastic grommets where the cables entered the PSU and they were the horrible hard plastic cable crimpers that do this:


Both the mains lead and power to the TRS80 lead were like this, so they got copped in case 40 years of crimping had damaged them. This is the output lead and you can see that the GND lead has come away. The white lead also came away, more on that in a minute.

Unfortunately, the transformer, with the PCB attached to it is epoxied into the PSU, so I decided to stop and have a cup of tea, stirred with an engineers spoon :)


The PCB on the top is retained by 2 metal tabs, so bending these out of the way, it was necessary to de-solder the 3 outputs from the transformer and the mains lead to be able to lift the board up and see where the output leads were soldered to:


You can clearly see the remains of the white wire that may have been pulled when I was removing the grommet. The black GND wire appeared to have been poorly soldered in, and was just hanging loose. Having cut the cable previously, I made sure to mark the positions before soldering the lead back to the PCB:


Note that I also had removed the live and neutral from the other side of the board, but it turned out it wasn't necessary. I then put the PCB back in it's original position, folded the tabs back and re-soldered the 3 transformer outputs, and my freshly tinned mains lead:



A quick test and all the voltages were now present at the plug :) So I tried the machine and we're off and running again:


It was then just a case of refitting the horrible crimpy grommets as I had no alternatives (Should be good for another 40 years :) ) and refitting the bottom plate, making sure all the cardboard/plastic insulation was back in it's original spot.

Well with the TRS-80 apart for the pre Quinnterface memory downgrade, it made sense to look at the other upgrade I'd been looking at, that being adding audio. Some software uses it, some doesn't, but the parts were cheap and it's a fun little project.

For me, aside from adding audio, like the ROM switch mod for FreHD, I wanted it to leave the case undamaged, so I needed to locate the amp control somewhere I could still turn it off/on and adjust the volume, so I opted to put it at about 45 degrees in the case pointing up towards the expansion slot, but far enough away to not get in the way:


So I can operate it with a long screwdriver, but didn't drill any holes. This picture belies just how far inside the case it is.

It's a little messy inside as everything is held in place with hot glue, but they key here is it's reversible:


And yes, I have 2 speakers, but it'll only be getting a mono signal, so the inputs will be tied together. I've since wired the power for the amp in, with a plug for easily disconnecting if/when I have it apart again, and all that's left is to make the audio connection. These will also have a plug to facilitate easy disconnection, but I've been at it a while today, what with finishing off the Electron, downgrading the TRS-80 RAM (Note the 16K Level II sticker by the expansion port is once again correct :) ) and putting the audio stuff in, so I think that'll get left for another day, as I need to go and double check just where the audio needs to be connected to the mainboard.

Good day overall though.

And the TRS is back together and running fine with 16KB of RAM and a new sound system :)


And according the the tracking, the QI should arrive tomorrow, but I'll believe it when I see it. Better than the original delivery estimate of 22nd December :)

:dualthumbup:

Nice repair and upgrade !

:cheers:

HigashiJun wrote: 04 Dec 2023 12:42 Nice repair and upgrade !

:cheers:

Thank you :)