Hiiii
I've just come to this forum and I've been quite welcome
The thing is that I was given a QL that, obviously, doesn't work. It has no PSU, and I buit one just taking a 9V PSU and using a special connector I could given the 9V to the QL:
But when I turn on the PSU, an excellent black screen is shown in the TV
And nothing else happens...
I did this twice. And the 2nd time it happened something: suddenly, a serie of random loud beeps sounded (I almost fall down from the chair)
This QL has no heat sink inside. Anyway, do you know where should I get measurements of volts as I can check if at least the voltages are OK?
Thanks in advance!
QL doesn't work: black screen
Re: QL doesn't work: black screen
(ooops, the pic doesn't fit the forum!!)
If something works... DON'T TOUCH IT!!! AT ALL!!!
- 1024MAK
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Re: QL doesn't work: black screen
The 7805 voltage regulator needs a heatsink in order for it to dissipate the heat it generates. If it does not have a suitable heatsink, it will shut down. However, running the QL like this risks damaging the 7805, as the sharp and rapid cool - heat cycle is not good for it.
As viewed in your picture, the left hand leg of the 7805 should be a DC voltage of at least 8.5V. The right hand leg should be between 4.75V and 5.25V. Both these voltages are respect to 0V which the centre leg and the heatsink tab on the 7805 are both connected.
I assume that you are aware that the power input is a three pin connector and as well as 9V DC, the QL requires a AC line so that two further voltage regulators can generate +12V and -12V rails. These are mainly used by the serial ports, but IIRC one of them is also used for something else (could be a mod that was recommended).
Edit: there is some power supply information in this thread. If you search you may well find more information.
Mark
As viewed in your picture, the left hand leg of the 7805 should be a DC voltage of at least 8.5V. The right hand leg should be between 4.75V and 5.25V. Both these voltages are respect to 0V which the centre leg and the heatsink tab on the 7805 are both connected.
I assume that you are aware that the power input is a three pin connector and as well as 9V DC, the QL requires a AC line so that two further voltage regulators can generate +12V and -12V rails. These are mainly used by the serial ports, but IIRC one of them is also used for something else (could be a mod that was recommended).
Edit: there is some power supply information in this thread. If you search you may well find more information.
Mark
Standby alert
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer in Somerset later in the year
QL, Falcon, Atari 520STFM, Atari 1040STE, more PC's than I care to count and an assortment of 8 bit micros (Sinclair and Acorn)(nearly forgot the Psion's)
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer in Somerset later in the year
QL, Falcon, Atari 520STFM, Atari 1040STE, more PC's than I care to count and an assortment of 8 bit micros (Sinclair and Acorn)(nearly forgot the Psion's)
Re: QL doesn't work: black screen
Yep, the thing is that this QL came without a heatsink... Do you know where can I find one? Or could I build one with pieces?1024MAK wrote:The 7805 voltage regulator needs a heatsink in order for it to dissipate the heat it generates. If it does not have a suitable heatsink, it will shut down. However, running the QL like this risks damaging the 7805, as the sharp and rapid cool - heat cycle is not good for it.
I'll see if these volts are ok in this QL, but I think so as the computer boots, but not the OS. I heard once a serial of beeps1024MAK wrote: As viewed in your picture, the left hand leg of the 7805 should be a DC voltage of at least 8.5V. The right hand leg should be between 4.75V and 5.25V. Both these voltages are respect to 0V which the centre leg and the heatsink tab on the 7805 are both connected.
OK, 1024MAK, I have no PSU for the QL so I had to build one for booting up at least. I thought that 12V were only used for microdrives, so I don't mind at the moment. I prefear now see if this QL works or not, I mean, if customs chips are dead or not.1024MAK wrote: I assume that you are aware that the power input is a three pin connector and as well as 9V DC, the QL requires a AC line so that two further voltage regulators can generate +12V and -12V rails. These are mainly used by the serial ports, but IIRC one of them is also used for something else (could be a mod that was recommended).
Thanks, 1024MAK, first of all I'll check the voltage in the 78051024MAK wrote: Edit: there is some power supply information in this thread. If you search you may well find more information.
If something works... DON'T TOUCH IT!!! AT ALL!!!
- vanpeebles
- Commissario Pebbli
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Re: QL doesn't work: black screen
In the past people have mounted the regulator on the outside of the case, fitted to an old PC heatsink or similar
Re: QL doesn't work: black screen
It's a good idea! Although I'll replace the regulator by a Tracopower, I can do that meanwhile
If something works... DON'T TOUCH IT!!! AT ALL!!!
Re: QL doesn't work: black screen
I've just measured the pins of the 7805, and it's okay:
IN: +8.8 VDC
OUT: +4.9 VDC
Which other pins could I measure to determine if chips are well fed?
IN: +8.8 VDC
OUT: +4.9 VDC
Which other pins could I measure to determine if chips are well fed?
If something works... DON'T TOUCH IT!!! AT ALL!!!
Re: QL doesn't work: black screen
I'd like but not yet, I'm looking for one since 2 years ago as I'm repairing Jamma boards too.
I only have a polymeter (is it well said?). By the moment I suspect that some chip is not receivig the right voltage. Which pins should be measured first of all?
EDIT: Ah, I forgot it, I also have a logical probe
I only have a polymeter (is it well said?). By the moment I suspect that some chip is not receivig the right voltage. Which pins should be measured first of all?
EDIT: Ah, I forgot it, I also have a logical probe
Last edited by Bubu on Tue Dec 09, 2014 12:17 am, edited 1 time in total.
If something works... DON'T TOUCH IT!!! AT ALL!!!
Re: QL doesn't work: black screen
Searching and searching and searching again I've found this:
http://www.sinclairql.net/srv/qlsm4.html
In a table is shown this:
TV/monitor screens black. Power light on. Fails to power-up. Check voltages (para 2.2.3)
Renew IC22
Renew IC24
Check RAMs
Renew IC34
Renew IC18
Renew IC33
So I have something that I can check I'll tell you the results!
Ah, the "power light", where is it? In the PSU or in the QL?
http://www.sinclairql.net/srv/qlsm4.html
In a table is shown this:
TV/monitor screens black. Power light on. Fails to power-up. Check voltages (para 2.2.3)
Renew IC22
Renew IC24
Check RAMs
Renew IC34
Renew IC18
Renew IC33
So I have something that I can check I'll tell you the results!
Ah, the "power light", where is it? In the PSU or in the QL?
If something works... DON'T TOUCH IT!!! AT ALL!!!