I use these schematics:
I found a cheap 9.5v power supply from amazon..
I'm planning to realize the following connections:
2 PIN 4 J8
4 PIN 2 J8
6 PIN 1 J10
1 PIN 6 J8
obviously all regulator are removed... I'm just testing that I have the right voltage on the entry of the regulator
I found 8.55v at the entry of the 5v regulator (not yet connected tested the entry of 12v regulator)
8.55 looks a little low for 9v but it's acceptable for the regulator I'm planing to use
7905 is definitively disconnected (ram already replaced by 4164)
7812 will be replaced by 5v regulator to bring 5v in 12v tracks
regulators I'm planning to use: http://www.ezsbc.com/index.php/featured-products-list-home-page/psu5.html#.WBSKT_mLSUk
I hope it's enough for the tape... (if the tape is not working I'll try to find an bette power supply)
looks ok for you ? I've not missed anything ?
to tell the truth I'm scared by analogic and power supplies :)
I'm not sure I follow; when you say -9V do you actually mean the ground return for the +9V, i.e. 0V? I don't see any need for -9V unless you want to connect J10-1&2, but connecting -9V to pin 9 would not be a good idea. If you have -9V available and want to connect it, use pin 1 or 5.
And why J8-6 to J10-1?
But you don't seem to be connecting to ground (pins 3 & 6) at all?
Maybe I'm missing something (again ;-) but it doesn't quite make sense to me.
Assuming you've left the original 5V regulator VR4 or replaced it with an equivalent, and replaced the 12V VR2 with another 5V regulator, then IMO all you'd need is +9V to pins 2 and 8 and ground to pins 3 and 6. That should also raise your cassette voltage above 9V.
Anybody see a flaw there before didier blows up his board?
I may have forgotten something...
I connected J8-6 to J10-1
in my connection -9 is becoming effectively the ground return
but -9v is not available on J8 but -9 is available on J10...
I dont really like this solution with a flying wire but it works
according to the schematics J10-3 and J10-6 are connected internally
with my 9.5v power supply unregulated 9v is around 8.7v and the 6v for the tape is too low :(
I'll probably change for a 12v power supply with 2 diodes added to drop around 10.6v
the board is working, the regulators can accept up to 20v on entry the real problem is 9v unregulated and 6v for the tape
I'll probably replace 10-1 by pin 2 of the 7905 (removed)
I'm also planning to add a protection against overvoltage, there
are so many power supply ending with the same jack...
On 01/11/2016 01:59, Mike Stein wrote:
I *am* looking at the schematic ;-D ...
Still seems awfully convoluted and the references to -9V (and now 6V) are certainly confusing.
I have no idea why you're using the -9V line as your ground instead of the existing ground connection; you will lower your voltage by ~.6V going through the bridges and probably overload J10, not meant for that much current.
You're supplying the main 5V to pin 1, then through the bridge (which wastes power and lowers your voltage by another ~.6V) to pin 4 and then finally to pin 2; as I said, why not just connect your 9V to pin 2 in the first place?
Connect +9V to pin 8, through CR4 to VR2 (now a 5V regulator) and you've got the 5V for the RAM.
Finally, connect ground (+9V return) to pins 3 and/or 6 and those are the only three connections needed IMO.
But since this is the third time I've suggested it I'll shut up; your way works for you and if you'd rather replace the supply instead, why not.
Hi if you don't mind me butting in:
Are you referring to 9V AC uses 2 wires doesn't it so if I'm thinking correctly theres
a hot wire and a neutral?
On Tue, Nov 1, 2016 at 10:11 AM, Mike Stein <[hidden email]> wrote:
Well, AC and DC both use 2 wires; I'm assuming that since he says 'power supply' instead of just 'transformer' we're talking about a DC supply...
'Hot' and 'neutral' are mainly used in reference to house wiring, where the neutral is usually connected to 'ground', a real connection to the earth, for safety reasons; aside from that connection there is really no difference between the two.
In the PET there are two AC sources; the 9V is a two-phase source, actually an 18V winding with a center tap to ground, that supplies both +9V and -9V through the bridge, while the 16V supply is floating and only the rectified 16V DC is connected to ground.
In reply to this post by traymond
the way the standard power supply is connected produce +9v and -9v
I'm not interested by -9v and my power supply bring 9.5v DC is
connected to produce GND / + 9v (actually 8.7) drop due to the
I'll improve it later to get a correct unregulated 9v
On 01/11/2016 19:58, Terry Raymond wrote:
Keep in mind that the listed voltages are nominal unregulated voltages; depending on line voltage the +9V is probably closer to +10V while the low load -9V is around -12V.
yes but I prefer to test with a lower voltage, check the result and increase according to these results
rather than trying a higher tension first, blow something and have to repair
I'll probably use a 12v DC power supply with one or two diodes to
lower the voltage
On 01/11/2016 22:25, Mike Stein wrote:
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