Search found 15 matches

by Popopo
Fri Sep 25, 2020 5:52 pm
Forum: Hardware
Topic: Searching for PCF1306P
Replies: 19
Views: 19042

Re: Searching for PCF1306P

Hello Popopo In the simulator, this charge pump circuit does work well and should have no problem supplying +12V for the colour encoding chip. I think the reason that Sinclair used a DC-DC converter based on an inductor (the ‘coil’) is because the 4116 (or equivalent) ‘lower’ DRAM chips use quite a...
by Popopo
Fri Sep 25, 2020 5:11 pm
Forum: Hardware
Topic: Searching for PCF1306P
Replies: 19
Views: 19042

Re: Searching for PCF1306P

Thanks for posting the NE555 based charge-pump circuit for generating the +12V supply. I have a question, I can’t make sense of the circuit around Q1. The circuitry for the base makes sense, it’s monitoring the voltage on the +12V supply. So I presume it’s intended function is to control the NE555 ...
by Popopo
Thu Sep 24, 2020 10:56 pm
Forum: Hardware
Topic: Searching for PCF1306P
Replies: 19
Views: 19042

Re: Searching for PCF1306P

Thanks for your reply bola_dor Don’t worry, I’ll work it out eventually... but not today :mrgreen: Mark 20200923_202643.jpg Ok Tr is conected to +5v . I marked in red points in continuity with 5v rail. Cian are GND And yellow and violet the other leads from Tr Tr is marked as 238B 20200923_203614.j...
by Popopo
Thu Sep 24, 2020 10:53 pm
Forum: Hardware
Topic: Searching for PCF1306P
Replies: 19
Views: 19042

Re: Searching for PCF1306P

20200920_232124.jpg Just to show how it looks.. This is a CZ Spectrum (argentinian clone) the board is a slightly modified ISSUE 6A, low ram is +5v only.. many of them had the PCF1306P but many others had this ZX8401 board. Perhaps because of lacking of stock... the first argentinian Spectrum CZ200...
by Popopo
Wed Sep 23, 2020 1:30 am
Forum: Hardware
Topic: Searching for PCF1306P
Replies: 19
Views: 19042

Re: Searching for PCF1306P

20200920_232124.jpg Just to show how it looks.. This is a CZ Spectrum (argentinian clone) the board is a slightly modified ISSUE 6A, low ram is +5v only.. many of them had the PCF1306P but many others had this ZX8401 board. Perhaps because of lacking of stock... the first argentinian Spectrum CZ200...
by Popopo
Fri Sep 11, 2020 1:26 am
Forum: WANTED
Topic: ZX81 ULA or ULA Replacement
Replies: 12
Views: 14007

Re: ZX81 ULA or ULA Replacement

Hello again, Sorry but I couldn't get all information about it. Please to check : http://blog.retroleum.co.uk/electronics-articles/nebula-spectrum-ula-chip-replacement-module/ May it helps you? write to Phill, he will answer you properly. The price is pretty low compared with other solutions. Cheer...
by Popopo
Sun Aug 30, 2020 11:34 pm
Forum: WANTED
Topic: ZX81 ULA or ULA Replacement
Replies: 12
Views: 14007

Re: ZX81 ULA or ULA Replacement

Hello again,
Sorry but I couldn't get all information about it.

Please to check : http://blog.retroleum.co.uk/electronics ... nt-module/
May it helps you? write to Phill, he will answer you properly.

The price is pretty low compared with other solutions.
Cheers
by Popopo
Sun Aug 30, 2020 2:25 pm
Forum: Hardware
Topic: Searching for PCF1306P
Replies: 19
Views: 19042

Re: Searching for PCF1306P

For the record, the PCF1306P is the upper RAM multiplexor. It is also known under the ZX8401 name and the Amstrad part number 40058. It was introduced in the issue 5 board 48K Spectrum, and also used on the 6A board Spectrum, the 128K Toastrack, and the +2 (grey). See also this topic . Mark That's ...
by Popopo
Sun Aug 30, 2020 1:52 pm
Forum: Hardware
Topic: lost in modifications 4A
Replies: 11
Views: 12646

Re: lost in modifications 4A

understood !! , i was referring to the capacity of the original caps which has changed after 36 years. but the condition of this spectrum shows is has been neglected for many years ,so a recap with fresh components will give me a more solid base for measuring the voltages . i hope the components wi...
by Popopo
Sun Aug 30, 2020 1:44 pm
Forum: Hardware
Topic: Searching for PCF1306P
Replies: 19
Views: 19042

Re: Searching for PCF1306P

Hi, Few members have contacted to me about the PFC replacement that I have. It was developed based on the work of J.L. we did it on SMD format. I have few board left (9) from the last stock that we produced (about 60+). The few 9 left, I published to sell by ebay site. Here is the link: PCF1306P rep...