Unless there were some obvious problem you can spot, I think the possibility of a faulty chip has to be considered.
But don't be under any illusions about an easy fix... I didn't think this would have gone this far tbh.
All you can realistically do (and this applies to any faulty equipment) is to check ALL the supplies are correct... and if you haven't a correct circuit then that means pulling the data sheets for all the IC's and seeing where the supplies are.
If it were me, I would consider the RAM suspect.
These are available,
Semiconductor: MN4264-15 (MN 4264-15) - 482220970422 IC PHILIPS...
or try and get a scrapper of ebay that uses the same chip set, then you have the SAA IC's too.
But don't be under any illusions about an easy fix... I didn't think this would have gone this far tbh.
All you can realistically do (and this applies to any faulty equipment) is to check ALL the supplies are correct... and if you haven't a correct circuit then that means pulling the data sheets for all the IC's and seeing where the supplies are.
If it were me, I would consider the RAM suspect.
These are available,
Semiconductor: MN4264-15 (MN 4264-15) - 482220970422 IC PHILIPS...
or try and get a scrapper of ebay that uses the same chip set, then you have the SAA IC's too.
I'll have to leave it for today... don't get your hopes up too much... the last thing I want is you to pour money into it and still not fix it.
The players an unknown... I'm guessing you don't know it's history, whether it's ever been worked on before etc... don't be under any illusions.
The SAA7310 chips are hard to come by and dear at around £50
http://www.chsinteractive.co.uk/electrical-components/misc/i-c-saa7310-philips.htm
Much better to get a donor machine. I think some Rotels used a similar chip set... the Philips based machines were used by many.
The players an unknown... I'm guessing you don't know it's history, whether it's ever been worked on before etc... don't be under any illusions.
The SAA7310 chips are hard to come by and dear at around £50
http://www.chsinteractive.co.uk/electrical-components/misc/i-c-saa7310-philips.htm
Much better to get a donor machine. I think some Rotels used a similar chip set... the Philips based machines were used by many.
Okay the DRAM is fine at 5.1volts on pin 9.
I tested the SAA and I am not sure that I am doing it 100% so want to run through and check:
1. negative lead on GND on the machine (same one I used testing the DRAM chip)
2. The positive lead on pin 5 and then on pin 28 separately
Is that correct?
If it is correct then I am getting weird readings on this chip (certainly not -5v)
pin 28 is giving 10mV
pin 5 is giving 620mV
I think that I am doing something wrong, help!!
I tested the SAA and I am not sure that I am doing it 100% so want to run through and check:
1. negative lead on GND on the machine (same one I used testing the DRAM chip)
2. The positive lead on pin 5 and then on pin 28 separately
Is that correct?
If it is correct then I am getting weird readings on this chip (certainly not -5v)
pin 28 is giving 10mV
pin 5 is giving 620mV
I think that I am doing something wrong, help!!
found the pin layout for my SAA7210 in my player, am I simply checking the supply voltage to it, and would that be pin 40?
wasnt sure what you meant by the -5v
SAA7210 Datasheet pdf - Decoder for compact disc digital audio system - Philips
wasnt sure what you meant by the -5v
SAA7210 Datasheet pdf - Decoder for compact disc digital audio system - Philips
This is getting confusing.
Supply on the RAM is OK... this IC is still favourite at the moment.
Your piccy shows an SAA7220. Supply here is pin 24 at 5volts, pin 12 as ground.
If the other chip is an SAA7210 then 5 volts on pin 40, ground on pin 20.
What's on pin 21 out of interest ?
I'm sure these will be OK... and I think the RAM would be favourite to to swap... but remember no guarantees.
Supply on the RAM is OK... this IC is still favourite at the moment.
Your piccy shows an SAA7220. Supply here is pin 24 at 5volts, pin 12 as ground.
If the other chip is an SAA7210 then 5 volts on pin 40, ground on pin 20.
What's on pin 21 out of interest ?
I'm sure these will be OK... and I think the RAM would be favourite to to swap... but remember no guarantees.
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