Searching for PCF1306P

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1024MAK
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Re: Searching for PCF1306P

Post by 1024MAK »

Is the lower RAM made up of eight x MCM4517 DRAM chips?

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 so as to reduce the output once the +12V supply gets to it’s normal value.

However the collector and emitter circuits don’t make sense to me. Is this how it is actually wired?
Is Q1 emitter actually connected to the +5V rail?

Mark
bola_dor
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Re: Searching for PCF1306P

Post by bola_dor »

1024MAK wrote: Wed Sep 23, 2020 7:19 pm Is the lower RAM made up of eight x MCM4517 DRAM chips?

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 so as to reduce the output once the +12V supply gets to it’s normal value.

However the collector and emitter circuits don’t make sense to me. Is this how it is actually wired?
Is Q1 emitter actually connected to the +5V rail?

Mark
Yes they are mcm4517p12 IC.
About the schematics is not mine. I took it from someone else. So I can't help with the design but it is supposed to be made from the actual board..
ZX80, CZ1000, CZ1500, CZ2000, CZ1000Plus, CZ Spectrum, Sinclair QL.
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1024MAK
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Re: Searching for PCF1306P

Post by 1024MAK »

Thanks for your reply bola_dor

Don’t worry, I’ll work it out eventually... but not today :mrgreen:

Mark
bola_dor
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Re: Searching for PCF1306P

Post by bola_dor »

1024MAK wrote: Wed Sep 23, 2020 9:00 pm 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.jpg
ZX80, CZ1000, CZ1500, CZ2000, CZ1000Plus, CZ Spectrum, Sinclair QL.
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Popopo
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Re: Searching for PCF1306P

Post by Popopo »

bola_dor wrote: Wed Sep 23, 2020 2:06 am
Popopo wrote: Wed Sep 23, 2020 1:30 am
bola_dor wrote: Mon Sep 21, 2020 4:28 am 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 CZ2000 was made under License with original issue 6A boards . This later model was not..
Wauuuu such a treasure!!! really nice. I guess both versions use the PCF system to address the memory.
But not idea if they are equal... unless you could replace the ZX8401 by the PCF1306P.

Really nice board, really, in fact I want to proceed to do my scheme to built my modified Issue6A board with some little changes...
What is inside the RF module?
thanks
the ZX8401 board is on a socket.. you can use the PCF1306P.. I have one with the IC actually..
RF modulator has two outputs, one RF PAL-B and the other is a composite output marked as monitor so you don't have to modify it :D
Board uses a lm555 to build 12v to the LM1891 and low ram is 4116 pin compatible but using +5v only..
FB_IMG_1600819488828.jpg
1331773652_857_FT66490_cz_elevador_tension_555.png
Amazing!!!
And very handful,
I am designing a test RAM and was not sure about how to generate +12v in a stable way... this one could be very useful, so thank you a lot for the information.
with a few of resistors!!! amazing modulator.
thanks
Let's do it
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Popopo
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Re: Searching for PCF1306P

Post by Popopo »

bola_dor wrote: Thu Sep 24, 2020 1:37 am
1024MAK wrote: Wed Sep 23, 2020 9:00 pm 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.jpg
Nice way to swift the coil!!! Nice
Let's do it
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1024MAK
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Re: Searching for PCF1306P

Post by 1024MAK »

1024MAK wrote: Wed Sep 23, 2020 7:19 pm 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 so as to reduce the output once the +12V supply gets to it’s normal value.

However the collector and emitter circuits don’t make sense to me. Is this how it is actually wired?
Is Q1 emitter actually connected to the +5V rail?
Hi all

I’ve put the details of the schematic for this (exactly as shown) into a SPICE (circuit simulation) application. It works in the simulation, so it appears that the schematic does reflect the actual circuit used.

Mark
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1024MAK
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Re: Searching for PCF1306P

Post by 1024MAK »

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 lot of power from the +12V supply. And of course they need a -5V supply as well.

In some 16k byte memory expansion ‘packs’ for the ZX81, Sinclair used a similar inductor based DC-DC converter. But other third party manufacturers used the “+9V” supply (with extra smoothing / decoupling capacitors) for the +12V supply to the 4116 DRAM chips. Taking advantage of the so called +9V supply actually being about 10.5V to 11.5V

They then used various different designs to get a -5V supply, some of which did use a charge pump. But most used a 5.1V Zener diode to stabilise the voltage on the -5V supply.

Mark
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Popopo
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Re: Searching for PCF1306P

Post by Popopo »

1024MAK wrote: Fri Sep 25, 2020 11:37 am
1024MAK wrote: Wed Sep 23, 2020 7:19 pm 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 so as to reduce the output once the +12V supply gets to it’s normal value.

However the collector and emitter circuits don’t make sense to me. Is this how it is actually wired?
Is Q1 emitter actually connected to the +5V rail?
Hi all

I’ve put the details of the schematic for this (exactly as shown) into a SPICE (circuit simulation) application. It works in the simulation, so it appears that the schematic does reflect the actual circuit used.

Mark
So great!!!
PSpice 9.1?

thank you
Let's do it
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Popopo
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Re: Searching for PCF1306P

Post by Popopo »

1024MAK wrote: Fri Sep 25, 2020 11:49 am 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 lot of power from the +12V supply. And of course they need a -5V supply as well.

In some 16k byte memory expansion ‘packs’ for the ZX81, Sinclair used a similar inductor based DC-DC converter. But other third party manufacturers used the “+9V” supply (with extra smoothing / decoupling capacitors) for the +12V supply to the 4116 DRAM chips. Taking advantage of the so called +9V supply actually being about 10.5V to 11.5V

They then used various different designs to get a -5V supply, some of which did use a charge pump. But most used a 5.1V Zener diode to stabilise the voltage on the -5V supply.

Mark
Hello 1024MAX.
The most part of what you explained is right.
Pay attention on the point that just in the first line of power there is a linear regulator DC 7805, so... we get 5 volts. The rest of voltage from the power supply is wasted and dismissed by the heat-sink But we need to get 12v and -5v, for that purpose they use TR4/TR5. The coil is used to increase the voltage to +12v and in line with it (capacitors, diodes... ) to made it stable.

Sinclair wanted as cheap as possible his Spectrums, that is why we have faulty high rams, ULA, etc. So a coil was a very cheap way at this time to get +12v but this design imply many extra problems... that is why we get fried many low and high RAMs and why the DC-DC circuit was changing along to the time and revisions of the board (issues X).

I am not an expert on it, maybe I am wrong about something but the focus is as I have told.
+9v from some supply...11 or more become from the Spanish power supply Investronica, that at that time designed the 128K and the case. The gave an extra power to get enough to feed some new components (later adopted for the Spectrum +2 gray), and also the interface EDGE, due to this one use to get too hot or even damage the ULA, ROM o RAM for power lack. I have a couple of those power supply. Also Sr. Clive thought it was enough with 1A to feed the whole Spectrum (a big mistake), I replaced all my 7508 with their heatsink for mini360 buck Step-Down, with 5v-2A working power. Reducing the consumption of the machine and ... the heat!!!! the big killer of Spectrum components (and membrane).

Thank you for checking the schema in your simulator, :)
Let's do it
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