Hi,
Yesterday the loudspeaker wires on my Cyrus II & PSX combo
made a shortcircuit and now it is quiet....... . I checked the transistors of the amp, looked OK, put in the fuses and it worked.
Check the PSX, dead, does anybody knows the schematic ?
I only see 2 transistors/regulators and some diodes.
gerald.
Yesterday the loudspeaker wires on my Cyrus II & PSX combo
made a shortcircuit and now it is quiet....... . I checked the transistors of the amp, looked OK, put in the fuses and it worked.
Check the PSX, dead, does anybody knows the schematic ?
I only see 2 transistors/regulators and some diodes.
gerald.
gfredriks said:
Gerald
The circuit of the PSX is basically the same as that of the power supply section of the Cyrus 1 (and 2). The schematic is on my website:
http://www.tcaas.btinternet.co.uk/cyrus1ps.gif
The main differences for the PSX are as follows:
The transformer is 27.9V-0-27.9V 240VA.
C65 and C66 are two 15000uF 50V slit foil capacitors in parallel.
D13, D14, D15 & D16 are two PFR852 diodes in parallel.
R113 & R114 are two 3k9 resistors in parallel.
F1 & F2 have a higher current rating.
It sounds as if you may have been lucky and that the fuses in the PSX blew before the output transistors. My experiences with the Cyrus 1 have been that the output transistors protect the rail fuses rather than the other way round.
Geoff
Hi,
I have not opened the PSX for the Cyrus11 but I think it only has the top half inside i.e, no regulated part.
But there are 5pins on the plug so there is something else coming out of there, but what does it supply?
The Cyrus output has some current limiting.
I guess the current limit triggered, protecting the output transistors. Then the PSX fuses overheated and opened.
I think the PSX fuses are F3.15A . Do not fit standard or T fuses.
Geoff,
when you said parallel, did you mean in series?
I have not opened the PSX for the Cyrus11 but I think it only has the top half inside i.e, no regulated part.
But there are 5pins on the plug so there is something else coming out of there, but what does it supply?
The Cyrus output has some current limiting.
I guess the current limit triggered, protecting the output transistors. Then the PSX fuses overheated and opened.
I think the PSX fuses are F3.15A . Do not fit standard or T fuses.
Geoff,
when you said parallel, did you mean in series?
AndrewT said:
The PSX has both the high current supply (for 'upgrading' the Cyrus 2) and the regulated output as it was also sold as an 'upgrade' for the Cyrus CD player.
The Cyrus 1 has F3.15A rail fuses and the Cyrus 2 has F4.0A so I would expect the PSX to have fuses of at least 4A and possibly higher. Unfortunately I didn't make a note of the fuse rating when I tool the lid off a friend's PSX a few years ago.
No, I meant parallel for the reservoir capacitors, for the rectifier diodes and for the capacitor discharge resistors.
Hi Guys,
Actually, these questions are easily answered as soon as Gerald pops the cover and has a look. I've not looked inside one of these for a few years. They almost never give trouble.
The newer PSX-R is really cool. It detects the unit and adjusts it's output voltage to suit. Neat eh?
-Chris
Actually, these questions are easily answered as soon as Gerald pops the cover and has a look. I've not looked inside one of these for a few years. They almost never give trouble.
The newer PSX-R is really cool. It detects the unit and adjusts it's output voltage to suit. Neat eh?
-Chris
Re: Re: Cyrus PSX dead
It's late here, but I'm pretty sure that the PSX transformer is 400VA or more.
Perhaps the Cyrus Two already has 240VA compared to the smaller Cyrus 1?
Martin.
(..........who loves to be right on small techical issues like this because I don't understand the more complex ones.)
Geoff said:
It's late here, but I'm pretty sure that the PSX transformer is 400VA or more.
Perhaps the Cyrus Two already has 240VA compared to the smaller Cyrus 1?
Martin.
(..........who loves to be right on small techical issues like this because I don't understand the more complex ones.)
Hi,
Thanks for the schematics, I thought it would be more complex
because of those voltage regulators, but this an independent circuit,
just for the CD output (+/- 18V).
Yes, you're right only one fuse was blown (T 5A),
after measuring the diodes and replacing the fuse,
it works again. This is really a huge transformer,
taking almost 30% of the contents of the PSX and
twice as big as the one in Cyrus2-amp.
But now that it works again, I have another challenge:
I own a Cyrus 1 and a Cyrus 2 amp, because I have a small room,
I do not need the higher power of C2 and I am happy with
the C1 performance. What I would like to try is Cyrus 1 + PSX.
As an experiment I can solder the supply wires between
the two, I can also try to find the original plug and solder that one in.
PSX delivers 38V, Cyrus 1 has a 30V railvoltage.
Since I cannot lower the PSX voltage,
I have to work with 38V and must adjust the idle current.
Although I know electronics, I'm more digital based
so I wonder if you guys know which resistor(s) to in/de-crease.
gerald.
Thanks for the schematics, I thought it would be more complex
because of those voltage regulators, but this an independent circuit,
just for the CD output (+/- 18V).
Yes, you're right only one fuse was blown (T 5A),
after measuring the diodes and replacing the fuse,
it works again. This is really a huge transformer,
taking almost 30% of the contents of the PSX and
twice as big as the one in Cyrus2-amp.
But now that it works again, I have another challenge:
I own a Cyrus 1 and a Cyrus 2 amp, because I have a small room,
I do not need the higher power of C2 and I am happy with
the C1 performance. What I would like to try is Cyrus 1 + PSX.
As an experiment I can solder the supply wires between
the two, I can also try to find the original plug and solder that one in.
PSX delivers 38V, Cyrus 1 has a 30V railvoltage.
Since I cannot lower the PSX voltage,
I have to work with 38V and must adjust the idle current.
Although I know electronics, I'm more digital based
so I wonder if you guys know which resistor(s) to in/de-crease.
gerald.
Hi,
you can probably build a clone of the PSX for less than what extra value PSX adds to the Cyrus 2 on the secondhand market.
Have a look at Ebay and see what price you can get for a 2 or a 2+psx.
The PSU, as you have seen, is just a transformer + rectifier + smoothing.
The caps in tha PSX are now very old and may not be performing at their best. They were of a make and type specifically selected to sound good.
You need to clone or replace with something equally good.
I have seen a report suggesting that the Cyrus 1 is suitable for conversion to 1+psx.
You have both, so it is easy for you to compare the device types and the mechanical layout. It should be easy to add a 5pin xlr socket in the same location and wire it in appropriately. If the PSX voltage is just a bit too high for the Cyrus1, then your clone can use a slightly lower voltage transformer i.e. 25Vac rather than 28Vac, but keep in mind these early Cyrus designs were specified for 8ohm use not 4ohm. By the way a modern 25Vac transformer that is rated for 230Vac mains is equivalent to 26Vac when running on 240Vac in the UK.
Low load impedance is more likely to kill the amp than running slightly higher voltage.
I would check into that T5A fuse. Can you find confirmation that T (anti-surge=time delay) is the appropriate type? Can you find confirmation that 5A is the appropriate value?
I have found that F5A supports peak output currents of up to 10A (when fitted to the supply rails after the main smoothing). That implies 80Vpk into 8r=400W into 8r. That is too high for a Cyrus1 or 2. Try F4A (<=250W into 8r) and see if you get any nuisance tripping. F3.15A gives <=150W into 8r)
you can probably build a clone of the PSX for less than what extra value PSX adds to the Cyrus 2 on the secondhand market.
Have a look at Ebay and see what price you can get for a 2 or a 2+psx.
The PSU, as you have seen, is just a transformer + rectifier + smoothing.
The caps in tha PSX are now very old and may not be performing at their best. They were of a make and type specifically selected to sound good.
You need to clone or replace with something equally good.
I have seen a report suggesting that the Cyrus 1 is suitable for conversion to 1+psx.
You have both, so it is easy for you to compare the device types and the mechanical layout. It should be easy to add a 5pin xlr socket in the same location and wire it in appropriately. If the PSX voltage is just a bit too high for the Cyrus1, then your clone can use a slightly lower voltage transformer i.e. 25Vac rather than 28Vac, but keep in mind these early Cyrus designs were specified for 8ohm use not 4ohm. By the way a modern 25Vac transformer that is rated for 230Vac mains is equivalent to 26Vac when running on 240Vac in the UK.
Low load impedance is more likely to kill the amp than running slightly higher voltage.
I would check into that T5A fuse. Can you find confirmation that T (anti-surge=time delay) is the appropriate type? Can you find confirmation that 5A is the appropriate value?
I have found that F5A supports peak output currents of up to 10A (when fitted to the supply rails after the main smoothing). That implies 80Vpk into 8r=400W into 8r. That is too high for a Cyrus1 or 2. Try F4A (<=250W into 8r) and see if you get any nuisance tripping. F3.15A gives <=150W into 8r)
gfredriks said:
IMO, there is little point in trying to connect the PSX to your Cyrus 1 because due to the higher supply rail voltage you would need to change the output transistors to ones similar to those used in the Cyrus 2 otherwise you run the risk of exceeding the transistors SOA (the PT7, alias BUV28, is only rated at 65W for case temperatures between 25 and 60degC).
If you change the output transistors you will effectively have a Cyrus 2 because the only difference between the 1 and the 2, apart from an improved phono stage and a beefier power supply, it the use of different output transistors (or paralleled PT7s in the earlier plastic cased Cyrus 2).
As Andrew has said, if you want to improve the power supply for the Cyrus 1 you would probably be better building one from scratch, using a higher VA rated toroid and larger reservoir capacitors but keeping a similar supply rail voltage to that of the standard Cyrus 1. This would better suit modern speakers that tend to have a lower minimum impedance.
Alternatively, as Carlos has indicated, you could use the PSX but lower the rail voltage using a regulator circuit, though this solution would lower the efficiency (more heat dissipated) and would require some additional heatsinks.
For what it's worth, in a side-by-side comparision of the Cyrus 1 and a Cyrus 2 + PSX in a small room and at moderate volume I much preferred the standard Cyrus 1. It had more delicacy, detail and finesse on my taste in music (acoustic jazz and baroque classical). In a larger room or at higher listening levels or with very low efficiency speakers, where a higher power output is required, the situation might be different.
For the later v07 (metal cased) versions of the Cyrus, the quiescent current for the output stage is set by the values of R81/R83 in one channel and R82/R84 in the other (see schematic linked below). The earlier versions had a preset (RV2/RV3) for adjusting Iq.
http://www.tcaas.btinternet.co.uk/cyrus1pwr.gif
Re: Re: Re: Cyrus PSX dead
According to the notes I made at the time I took the lids off my friend's Cyrus 2 and PSX, the transformers were labelled 200VA and 240VA respectively, compared with 100VA for the Cyrus 1.
I remember thinking at the time that, if the phono stage was not being used, the PSX seemed rather expensive for the benefit of an extra 40VA plus some larger reservoir capacitors. However, if the phono stage is being used, the separation of the supplies to the power amp section and the phono stage is probably worthwhile.
Sonusthree said:
According to the notes I made at the time I took the lids off my friend's Cyrus 2 and PSX, the transformers were labelled 200VA and 240VA respectively, compared with 100VA for the Cyrus 1.
I remember thinking at the time that, if the phono stage was not being used, the PSX seemed rather expensive for the benefit of an extra 40VA plus some larger reservoir capacitors. However, if the phono stage is being used, the separation of the supplies to the power amp section and the phono stage is probably worthwhile.
Hi,
I would NOT recommend adding a regulator to any power amplifier and certainly not this one.
The expertise needed to get the pair to work properly AND sound good probably exceeds that available from most amplifier designers in this world. It is an enormous design exercise and even bigger development project that requires resources aplenty.
Cyrus are renowned for good sound at good value pricing.
Don't upset the applecart in an attempt to find the lone orange.
I would NOT recommend adding a regulator to any power amplifier and certainly not this one.
The expertise needed to get the pair to work properly AND sound good probably exceeds that available from most amplifier designers in this world. It is an enormous design exercise and even bigger development project that requires resources aplenty.
Cyrus are renowned for good sound at good value pricing.
Don't upset the applecart in an attempt to find the lone orange.
buv28 SOAR
Hi,
just looked at the SOA of the BUV28 device.
15W at 30 to 40Vce.
This is a very delicate power device. The next line at 10mS is much better @ 80W, pity there is no 100mS data.
Take great care to never overload and/or overheat it with dificult loads or resistricted cooling.
Very definately a domestic HiFi amplifier not suited to partying.
The description says fast switching.
Is there any data on Ft to allow comparison to newer devices?
Hi,
just looked at the SOA of the BUV28 device.
15W at 30 to 40Vce.
This is a very delicate power device. The next line at 10mS is much better @ 80W, pity there is no 100mS data.Take great care to never overload and/or overheat it with dificult loads or resistricted cooling.
Very definately a domestic HiFi amplifier not suited to partying.
The description says fast switching.
Is there any data on Ft to allow comparison to newer devices?
............. and for anyone considering a clone.
Here's a pic of the PSX Board.
Any cloners should note that part of this circuit on the left with the regulators and blue caps is for the low voltage output intended for the Mission PCM II CD player.
The PSX pictured here is one of the last ones with magnesium (?) alloy case AND toggle switch.
Cheers,
Martin.
Here's a pic of the PSX Board.
Any cloners should note that part of this circuit on the left with the regulators and blue caps is for the low voltage output intended for the Mission PCM II CD player.
The PSX pictured here is one of the last ones with magnesium (?) alloy case AND toggle switch.
Cheers,
Martin.
Attachments
AndrewT said:
Hi Andrew,
These pics were just old ones that I found on this computer and thought may be useful here. The lid is currently on again. I will be opening it up again soon to check the suitability of the replacement Mundorf caps.
I will check the circuit topology and post my findings. I would also learn a lot in the process. I have read alot about snubbers but never seen one in the wild!!
I can say that the four large caps are Cyrus slit foil 15000uF each at 50 Volts. I really wish I had the equipment to test them. Could Cyrus be right? Could they really be within spec after ~15 years? This is the biq question for me. Are older slit foils better than new Mundorf? I'll have to pay to find out.
N.B.
I've just breadboarded an opamp buffer/Baffle step compensation type circuit and have no other suitable permanent power supply except for a +/- 12V bench supply. I'm going to try the +/- 18V regulated output from the PSX to see how it does.
Cheers,
Martin.
I will have a look & take some better pics later but I believe that within that bundle of orange and red wires and plugs are..............................................................................
Black sheathed L and N (Blue and Brown) mains cable coming from the rear to the board.
Brown and red twisted wires leave the board to the transformer primary.
Yellow white and grey are transformer secondaries.
The orange and red wires go to the mains switch and back again to the board.
Small gauge red and black to the front LED.
The wires on the left hand side are the +/- 40v and +/- 18 v outputs going to the rear.
Sorry for stating the obvious in places,
Martin.
Black sheathed L and N (Blue and Brown) mains cable coming from the rear to the board.
Brown and red twisted wires leave the board to the transformer primary.
Yellow white and grey are transformer secondaries.
The orange and red wires go to the mains switch and back again to the board.
Small gauge red and black to the front LED.
The wires on the left hand side are the +/- 40v and +/- 18 v outputs going to the rear.
Sorry for stating the obvious in places,
Martin.