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Sounds about right there @rubber_jonnie. I’ve changed the ram in three TI-99s now and all had that kind of failure rate.

PhilC wrote: 15 Sep 2023 14:59 Sounds about right there @rubber_jonnie. I’ve changed the ram in three TI-99s now and all had that kind of failure rate.

Yeah, it's not good, but I know from my TRS-80 I had a similar failure rate, and I upgraded to 64K and did away with the negative voltages.

They at least all came out cleanly, so just a case of soldering in the sockets and modding the 4164s to go in their place.

4116 DRAMs were old and outdated technology in 1981, but they were relatively cheap. That's the only reason manufacturers still used them.

The 4164s were leading edge in the early 80s and had quite a high failure rate during manufacture, so they were expensive. Of cause we know how OKI managed to recover some of their costs by selling half working chips as 32Kx1.

stephen_usher wrote: 15 Sep 2023 22:04 Of cause we know how OKI managed to recover some of their costs by selling half working chips as 32Kx1.

Quite the smart move.

stephen_usher wrote: 15 Sep 2023 22:04 4116 DRAMs were old and outdated technology in 1981, but they were relatively cheap. That's the only reason manufacturers still used them.

The 4164s were leading edge in the early 80s and had quite a high failure rate during manufacture, so they were expensive. Of cause we know how OKI managed to recover some of their costs by selling half working chips as 32Kx1.

Old good times where all was possible...

:)

HigashiJun wrote: 16 Sep 2023 05:03

stephen_usher wrote: 15 Sep 2023 22:04 4116 DRAMs were old and outdated technology in 1981, but they were relatively cheap. That's the only reason manufacturers still used them.

The 4164s were leading edge in the early 80s and had quite a high failure rate during manufacture, so they were expensive. Of cause we know how OKI managed to recover some of their costs by selling half working chips as 32Kx1.

Old good times where all was possible...

:)

Well, let's be honest, Sinclair made these things cheaply and by using components that were available and at bargain basement prices they were able to sell the Spectrum for £175 for the 48K model compared to £335 for a BBC B 32K.

Which is why I had a Spectrum 48K (And a ZX81 before that) and not a BBC B, which we just couldn't afford. Also why Sinclair sold bucket loads of Spectrums, even the 16K models.

In fact I don't think I had any friends (At our computer club) who had a BBC B, as they were seen as a computer for the school, not the home. Most folks had Spectrums, Dragons, VIC-20's, C64s, Atari's, TRS-80 etc even though some of those were nearly as expensive as a BBC.

It was an incredible time, I saw so many computers come and go in the 80's and 90's.

The BBC B was £399 at the time that the Spectrum was £175. The Beeb price came down a long time after the Speccy dropped in price, I think in '84, to try to boost sales. (The speccy price drop happened a week after we'd bought my 16K machine for £125. *sigh*)

I had a couple of friends who had Beebs. One got one of the first Model As and upgraded it to have a floppy interface and 32K. The Beeb owned by the other friend I rescued from his Dad's house last year.

stephen_usher wrote: 16 Sep 2023 11:04 The BBC B was £399 at the time that the Spectrum was £175. The Beeb price came down a long time after the Speccy dropped in price, I think in '84, to try to boost sales. (The speccy price drop happened a week after we'd bought my 16K machine for £125. *sigh*)

Yes, £335 was the release price, but you're right, it did go up to £399 when they realised the costs were higher than planned. I think the Model A also went up from £235 to £299. You must have been gutted to see the 48K price drop just a week after you got a 16K machine. Did you upgrade it?

stephen_usher wrote: 16 Sep 2023 11:04 I had a couple of friends who had Beebs. One got one of the first Model As and upgraded it to have a floppy interface and 32K. The Beeb owned by the other friend I rescued from his Dad's house last year.

Yeah, I recall you mentioning that, good rescue :)

Just picked up an Issue 4s mainboard off eBay for spares, £20, it may help me with mine, which is also a 4s.

rubber_jonnie wrote: 16 Sep 2023 11:47 Just picked up an Issue 4s mainboard off eBay for spares, £20, it may help me with mine, which is also a 4s.

That sounds like a good idea, maybe transfer everything across once you’ve checked it.