Museum readying a TRS-80 model-1 - Revision history

Mahjongg: /* Re-assembled the painted TRS-80 model 1 */

2024-10-01T22:48:58Z

Re-assembled the painted TRS-80 model 1

← Older revision		Revision as of 22:48, 1 October 2024
Line 86:		Line 86:
	but the power is a much larger problem the TRS-80 needs both AC and DC power. pin 2 and 4 needed 19.8V DC 0.35A but also it needed AC, 17.0V AC 1A between pins 1 and 3. I do not know the polarity of the DC. So I gave up trying to power the TRS-80 Model 1, its just a showroom model. I think it is now of museum quality, see the picture below		but the power is a much larger problem the TRS-80 needs both AC and DC power. pin 2 and 4 needed 19.8V DC 0.35A but also it needed AC, 17.0V AC 1A between pins 1 and 3. I do not know the polarity of the DC. So I gave up trying to power the TRS-80 Model 1, its just a showroom model. I think it is now of museum quality, see the picture below

	One of the 1977 Trinity, the TRS-80 model I		'''One of the 1977 Trinity, the TRS-80 model I'''

	[[File:TRS-80 motherboard museum quality.JPG\|1000px]]		[[File:TRS-80 motherboard museum quality.JPG\|1000px]]

Mahjongg: /* Re-assembled the painted TRS-80 model 1 */

2024-10-01T22:48:31Z

Re-assembled the painted TRS-80 model 1

← Older revision		Revision as of 22:48, 1 October 2024
Line 85:		Line 85:

	but the power is a much larger problem the TRS-80 needs both AC and DC power. pin 2 and 4 needed 19.8V DC 0.35A but also it needed AC, 17.0V AC 1A between pins 1 and 3. I do not know the polarity of the DC. So I gave up trying to power the TRS-80 Model 1, its just a showroom model. I think it is now of museum quality, see the picture below		but the power is a much larger problem the TRS-80 needs both AC and DC power. pin 2 and 4 needed 19.8V DC 0.35A but also it needed AC, 17.0V AC 1A between pins 1 and 3. I do not know the polarity of the DC. So I gave up trying to power the TRS-80 Model 1, its just a showroom model. I think it is now of museum quality, see the picture below

			One of the 1977 Trinity, the TRS-80 model I

	[[File:TRS-80 motherboard museum quality.JPG\|1000px]]		[[File:TRS-80 motherboard museum quality.JPG\|1000px]]

Mahjongg: /* Re-assembled the painted TRS-80 model 1 */

2024-10-01T22:46:28Z

Re-assembled the painted TRS-80 model 1

← Older revision		Revision as of 22:46, 1 October 2024
Line 86:		Line 86:
	but the power is a much larger problem the TRS-80 needs both AC and DC power. pin 2 and 4 needed 19.8V DC 0.35A but also it needed AC, 17.0V AC 1A between pins 1 and 3. I do not know the polarity of the DC. So I gave up trying to power the TRS-80 Model 1, its just a showroom model. I think it is now of museum quality, see the picture below		but the power is a much larger problem the TRS-80 needs both AC and DC power. pin 2 and 4 needed 19.8V DC 0.35A but also it needed AC, 17.0V AC 1A between pins 1 and 3. I do not know the polarity of the DC. So I gave up trying to power the TRS-80 Model 1, its just a showroom model. I think it is now of museum quality, see the picture below

	File:TRS-80 motherboard museum quality.JPG		[[File:TRS-80 motherboard museum quality.JPG\|1000px]]

Mahjongg: /* Re-assembled the painted TRS-80 model 1 */

2024-10-01T22:45:30Z

Re-assembled the painted TRS-80 model 1

← Older revision		Revision as of 22:45, 1 October 2024
Line 84:		Line 84:
	The first obstacle can be overcome,although the TRS-80 used a very special method to use a TV for a monitor, the TV they used had a "hot chassis", that is all touchable metal parts of the TV were directly connected to mains voltage, but because on a TV only the antenna input was touchable, and that was save because there was a very small (a few picofarad) high voltage capacitor in series, but that could not be the case for a monitor, so tandy used a special trick to isolate the high voltage fron the computer, in the monitor was a small pcb with a few opto isolators powered from the computer that dis the isolation. But I found out that you could get a composite video signal from the 5V DIN connector regardlessly. you can make a working vide cable by using pin 4 for video, and pin 5 for gnd, and use either a SCART, or the yellow video input of a composite monitor.		The first obstacle can be overcome,although the TRS-80 used a very special method to use a TV for a monitor, the TV they used had a "hot chassis", that is all touchable metal parts of the TV were directly connected to mains voltage, but because on a TV only the antenna input was touchable, and that was save because there was a very small (a few picofarad) high voltage capacitor in series, but that could not be the case for a monitor, so tandy used a special trick to isolate the high voltage fron the computer, in the monitor was a small pcb with a few opto isolators powered from the computer that dis the isolation. But I found out that you could get a composite video signal from the 5V DIN connector regardlessly. you can make a working vide cable by using pin 4 for video, and pin 5 for gnd, and use either a SCART, or the yellow video input of a composite monitor.

	but the power is a much larger problem the TRS-80 needs both AC and DC power. pin 2 and 4 needed 19.8V DC 0.35A but also it needed AC, 17.0V AC 1A between pins 1 and 3. I do not know the polarity of the DC. So I gave up trying to power the TRS-80 Model 1, its just a showroom model. I think it is now of museum quality, see the picture below/		but the power is a much larger problem the TRS-80 needs both AC and DC power. pin 2 and 4 needed 19.8V DC 0.35A but also it needed AC, 17.0V AC 1A between pins 1 and 3. I do not know the polarity of the DC. So I gave up trying to power the TRS-80 Model 1, its just a showroom model. I think it is now of museum quality, see the picture below

			File:TRS-80 motherboard museum quality.JPG

Mahjongg: /* Memory */

2024-10-01T22:43:13Z

Memory

← Older revision		Revision as of 22:43, 1 October 2024
Line 79:		Line 79:
	I noticed the main +5 TO-03 Voltage regulator seems to have overheated. And I want to be sure the main regulator the MC1723 is still okay.		I noticed the main +5 TO-03 Voltage regulator seems to have overheated. And I want to be sure the main regulator the MC1723 is still okay.

	/* Re-assembled the painted TRS-80 model 1 /*		== Re-assembled the painted TRS-80 model 1 ==

			I decided not to try to get this TRS-80 working again, the reasons are that there are two large obstacles, first I do not have the original monitor, and secondly I do not have the power supply brick.
			The first obstacle can be overcome,although the TRS-80 used a very special method to use a TV for a monitor, the TV they used had a "hot chassis", that is all touchable metal parts of the TV were directly connected to mains voltage, but because on a TV only the antenna input was touchable, and that was save because there was a very small (a few picofarad) high voltage capacitor in series, but that could not be the case for a monitor, so tandy used a special trick to isolate the high voltage fron the computer, in the monitor was a small pcb with a few opto isolators powered from the computer that dis the isolation. But I found out that you could get a composite video signal from the 5V DIN connector regardlessly. you can make a working vide cable by using pin 4 for video, and pin 5 for gnd, and use either a SCART, or the yellow video input of a composite monitor.

			but the power is a much larger problem the TRS-80 needs both AC and DC power. pin 2 and 4 needed 19.8V DC 0.35A but also it needed AC, 17.0V AC 1A between pins 1 and 3. I do not know the polarity of the DC. So I gave up trying to power the TRS-80 Model 1, its just a showroom model. I think it is now of museum quality, see the picture below/

Mahjongg: /* Memory */

2024-10-01T22:22:11Z

Memory

← Older revision		Revision as of 22:22, 1 October 2024
Line 78:		Line 78:
	I have not powered up the computer yet, I want to be careful, and examine the schematics first.		I have not powered up the computer yet, I want to be careful, and examine the schematics first.
	I noticed the main +5 TO-03 Voltage regulator seems to have overheated. And I want to be sure the main regulator the MC1723 is still okay.		I noticed the main +5 TO-03 Voltage regulator seems to have overheated. And I want to be sure the main regulator the MC1723 is still okay.

			/* Re-assembled the painted TRS-80 model 1 /*

Mahjongg: /* Memory */

2024-09-03T22:29:15Z

Memory

← Older revision		Revision as of 22:29, 3 September 2024
Line 74:		Line 74:
	[[File:TRS-80 motherboard TOP side.JPG\|1000px]]		[[File:TRS-80 motherboard TOP side.JPG\|1000px]]

	One other problem many people opted to address is that the model-1 did not support lowercase letters, the designers chose a spare a few dimes by only using seven M2102 1K x 1-bit static RAM chips for video RAM. So a patch to install the missing RAM chip was quite common, and this user seems to have done the ~~ame~~ thing. the small rectangular PCB seems to indicate this is the case.		One other problem many people opted to address is that the model-1 did not support lowercase letters, the designers chose a spare a few dimes by only using seven M2102 1K x 1-bit static RAM chips for video RAM. So a patch to install the missing RAM chip was quite common, and this user seems to have done the same thing. the small rectangular PCB seems to indicate this is the case.

	I have not powered up the computer yet, I want to be ~~carefull~~, and examine the schematics first.		I have not powered up the computer yet, I want to be careful, and examine the schematics first.
	I noticed the main +5 TO-03 Voltage regulator seems to have overheated. And I want to be sure the main regulator the MC1723 is still okay.		I noticed the main +5 TO-03 Voltage regulator seems to have overheated. And I want to be sure the main regulator the MC1723 is still okay.

Mahjongg: /* Memory */

2024-09-03T22:27:06Z

Memory

← Older revision		Revision as of 22:27, 3 September 2024
Line 77:		Line 77:

	I have not powered up the computer yet, I want to be carefull, and examine the schematics first.		I have not powered up the computer yet, I want to be carefull, and examine the schematics first.
	I noticed the main +5 TO-03 Voltage regulator seems to have overheated .		I noticed the main +5 TO-03 Voltage regulator seems to have overheated. And I want to be sure the main regulator the MC1723 is still okay.

Mahjongg: /* Memory */

2024-09-03T22:24:01Z

Memory

← Older revision		Revision as of 22:24, 3 September 2024
Line 67:		Line 67:
	== Memory ==		== Memory ==

			A normal TRS-80 main mother board contains 16K DRAM, and needs and "expansion interface" to add another two banks of 16K DRAM chips for the 48K RAM that BASIC 2 expects.
			the previous user probably did not want to buy the very expensive expansion interface and knew that it was possible to replace the uPD4116 16K x 1-bit with uPD4164 64K x 1-bit chips. I knew that this could be done because I have modified dozens of TRS-80 model 1 computers myself in the early 80's. because the uPD4116's use thre different voltages, and the more modern uPD4164's use only +5V, you have to remove some decoupling caps, and wiring .

			You can see the patch wiring for this patch from the solder-side of the PCB:

			[[File:TRS-80 motherboard TOP side.JPG\|1000px]]

			One other problem many people opted to address is that the model-1 did not support lowercase letters, the designers chose a spare a few dimes by only using seven M2102 1K x 1-bit static RAM chips for video RAM. So a patch to install the missing RAM chip was quite common, and this user seems to have done the ame thing. the small rectangular PCB seems to indicate this is the case.

	~~A normal TRS-80 main mother board contains 16K DRAM~~, ~~and needs and "expansion interface" to add another two banks of 16K DRAM chips for the 48K RAM that BASIC 2 expects.~~		I have not powered up the computer yet, I want to be carefull, and examine the schematics first.
	~~the previous user probably did not~~ want to ~~buy the very expensive expansion interface~~ and ~~knew that it was possible to replace~~ the ~~uPD4116 16K x 1-bit with uPD4164 64K x 1-bit chips~~. I ~~knew that this could be done because I have modified dozens of TRS-80 model 1 computers myself in~~ the ~~early 80's. because the uPD4116's use thre different voltages, and the more modern uPD4164's use only~~ +~~5V, you~~ have ~~to remove some decoupling caps, and wring~~ .		I noticed the main +5 TO-03 Voltage regulator seems to have overheated .

Mahjongg: /* The mother board */

2024-09-03T22:13:27Z

The mother board

← Older revision		Revision as of 22:13, 3 September 2024
Line 62:		Line 62:
	looking at the TRS-80 Motherboard you can see that it was extensively repaired and modified.		looking at the TRS-80 Motherboard you can see that it was extensively repaired and modified.
	The mother board is mounted inside the case with the components hanging down on the board, so that the keyboard can rest on the bottom of the PCB with some wide round rubber standoffs. One modification that is immediately obvious is that that the short FLEX-PCB connection between the Motherboard amd the keyboard PCB. A known weakness in the design of the TRS-80 is a broken connection cable between the main and keyboard PCB. The previous owner aware of this problem has decided to take drastic actions, and replaced the short and breakabl cable with a much longer and more supple flexcable.		The mother board is mounted inside the case with the components hanging down on the board, so that the keyboard can rest on the bottom of the PCB with some wide round rubber standoffs. One modification that is immediately obvious is that that the short FLEX-PCB connection between the Motherboard amd the keyboard PCB. A known weakness in the design of the TRS-80 is a broken connection cable between the main and keyboard PCB. The previous owner aware of this problem has decided to take drastic actions, and replaced the short and breakabl cable with a much longer and more supple flexcable.

			[[File:TRS-80 motherboard bottom side.JPG\|1000px]]

	== Memory ==		== Memory ==