Why are these fuses blowing

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The PT7 devices are probably a standard device that Cyrus mark up with their own number. TIP41C have been used in many nice amplifiers and should be fine. If you wanted to go better than that you may be able to find a suitable Japanese 2SCxxxx device, but these are generally hard to find. If you buy all the transistors as I suggested you will be in for a bill of about £10.

Can you give a clue as to how the amp blew? Was it broken when you got it?
 
I got the amp off my uncle, but apparently it worked well when he used it last (3 years ago).

Have put the amp into a shop to get repaired - as not overly confidant that I wouldn't solder the surrounding components together when replacing the transistors.

When I get it back is there any special way everything should be connected? To avoid blowing anything else?

There seems to be only one output for the speakers but my Linn Kaber LS500's have 3 left and right inputs and can be bi/tri and single wired/amped by means of shifting some plates. I only have the one amp though, so does this mean I just single wire them ie one plate over all three left and the other over all three right at each speaker?

Thanks again for all the help and advice

Darin
 
If it was working fine when you were given it then I think you may have damaged it by putting the amp unit fuses in :( I am surprised though that this did anything to the output stage, most likely it would damage the PSU capacitors and/or rectifier diodes.

To bi- or tri-wire your speakers all you need to do is join all 2/3 wires into one 4mm banana plug at the amp end. Then remove the plates on the speaker and wire the separate connections.
 
It would seem that I do not fully understand this single/bi & tri wiring.

My amp only has one set of red and black outputs for each of the left and right speakers. The Kabers have 3 sets of red and black inputs per speaker.

So from this info can I bi and tri wire with what I have? (obviously I would need more cable). If so are you saying that removing the plates and running three separate sets of wires for a speaker back into the amp ie 3 cables going into each banna plug - that I will improve the sound? It seems the same as having the plates on and running just the one set of wires as everything is connected to each other anyway.

Must remind you that I am an amatuer to all this so what may seem obvious to you is not for me.

I have recieved the Cyrus units back and its all go. The cyrus/kaber combination produces an awesome sound - I'm very impressed.

Thanks again for all the advice
 
One other query you may be able to help with -

When the Cyrus II and the Cyrus PSX units are conected and music is coming from the speakers, if I switch both units off the sound fades after about 30 seconds. If I switch only one or the other off the music still stays the same (as long as any one of the units power switch is on). And most bizzare when I switch off and disconnect the Cyrus PSX unit completely there is no difference.

This makes absolutely no sense to me, can you explain why and what the Cyrus PSX does or is supposed to do.

Cheers
Darin
 
So from this info can I bi and tri wire with what I have? (obviously I would need more cable). If so are you saying that removing the plates and running three separate sets of wires for a speaker back into the amp ie 3 cables going into each banna plug - that I will improve the sound? It seems the same as having the plates on and running just the one set of wires as everything is connected to each other anyway.

Indeed, you can bi- or tri-wire just with what you have, plus more cable. I'm not saying it will improve the sound, some people claim it makes a difference, that's all. Note that what you may percieve as differences to the sound by bi- or tri-wiring may actually be down to the simple fact that you have more cable capacity going to the speaker. To confirm this, leave all the cables connected and put the shorting plates on again.

Regarding the PSX, the main amp power switch is redundant when the PSX is connected. The PSX just substitues a more beefy power supply than the main amp one.
 
Cheers

And why are the 2 fuses removed? I had a look inside the Cyrus II now that it has been repaired and the repair man has put 2 fuses in where there were none before. Do I need to remove these, because as it is at the mo I can unplug the PSX unit completely and nothing changes.
 
Hi Darin,

I don’t know the Mission units, but I suspect that to upgrade the basic amplifier with the external PSX you need to disable the amplifiers internal PSU by removing the 2 fuses that had blown when you inserted the PSX.

Its sounds like your uncle had the PSX’s for the CD player or another amplifier (did he have a Bi-Amp system)?

I had a swift look at the Cyrus 1 circuit at the link posted ealier, and the fuses to the Power Amp stage are after the supply feed the Pre-Amp and LED, so even if the fuses blow to the power stage, the front panel lights will still come on – guess the same for the PSX.

I’m guessing that the “Repair Man” replaced the fuses in your amplifier, so it’s operating from its internal supply – while the fuses in the PSX PSU are still dead – or missing?

To operate the Amplifier from the PSX, remove the fuses internal in the Amp, and fit them to the PSX if they are missing or blown in the PSX - as I guess they are (first check PSX fuse rating and type).

:att'n: As I said, I wish to make very clear that I don’t know the units or their designs – so this is only an educated guess – risk is yours :att'n:

John
 
Oh dear :rolleyes:

You must not run the PSX with the amp internal fuses in place, as you are making the two power supplies fight each other, possibly damaging one or even both.

This is why removing the PSX makes no difference when all the fuses are in place.

:att'n: I would check the fuses in the PSX before going any further as you may have blown them or even damaged the unit itself.

If you have a voltmeter check for +40 and -40 volts relative to the ground pin on the PSX power output plug. If all is well then check that you haven't blown the amp power supply by hooking up a turntable and seeing if it sounds OK. (The turntable pre-amp runs off the amp power supply even if the PSX is used.)
 
:xeye: Oops, not that I knew he had put them in though. As I read your reply I ran to my system and turned it off at the wall. I removed the 2 fuses and the power lead from the Cyrus II unit. Checked the fuses in the PSX - fine and reassembled and reconected with the one power lead to the PSX. A slight moment of relief :D as music streamed from my speakers.

I don't have a record player to test the phono stage but assume all is ok. Have to admit that I didn't notice a change in sound quality or amplification.

Do you think everything is as it should be? Should I try and test the phono stage somehow? At the risk of offending someone, is it possible to connect the CD to it?

Thanks alot I think you may have saved me going back to a repairman - or worse having to buy a new amp!

Cheers
Darin
 
Hi Darin,

You still need to have the mains leads to both your Amp and PSX, as the Amps internal PSU still powers the pre-amp section - although according to the Cyrus 1 circuit (link posted ealier) the CD input is purely passive, with only the Phono input needing power - and front panel "Power" LED :)

Its a shame that you cannot split (maybe you can?) the PSU between channels, with say the AMP's internal supply powering one channel, while the external PSX powers the second channel - as when using the "line level" inputs (all inputs apart from Phono), the amps PSU does not "power" the pre-amp section, so is "wasted"

John
 
You can run the amp without a mains lead at all if you never intend to connect a turntable as the amp PSU only supplies power to the pre-amp when the PSX is used.

A CD player will have too high output for the turntable input. You may be able to get away with an old tuner or tape deck, but the chances of a distorted output are high. I would suggest hooking up a walkman with the headphones level turned way down. The sound will be over-bassy and dull, but you are not listening for tonal balance you are listening for distortion. If the pre-amp or PSU is damaged it will be quite obvious.
 
I tested the phono stage with a minidisk at low volume.

The Cyrus II unit has 2 inputs for the phono section, 1 - 'phono' and the other 'moving magnet'. I tried both.

The phono one had high bassy 'hiss' with normal music sound coming through from behind that (if you know what I mean). The second 'moving magnet, stage was definately very bassy (could see the top drive units of the speakers moving through the lycra covers with even low volume).

Both the phono stages produced sound with the input selector knob at the same selection (P). This makes me wonder what the O is for. (Selector positions being P,O,D,T,T. D being CD, T - Tuner, T - Tape)

When you say it will be quite noticeable when it is not right, what do you mean? From the test I was appalled at the sound that was produced but think that it was just a test as not a proper turntable and therefore was O.K.

What do you think from these results?
 
The tonal quality will be skewed by the EQ of the phono stage, so don't worry about that. What I am trying to get you to listen for is if there is any bad distortion or clipped, scratchy, grating sound. It really should be quite obvious if it is there. This will occur if one side of the power supply has been taken out by your PSX adventures, therefore only one half of the music signal is being played.

So if you get sound that is all there, just tonally wrong then it's probably OK.
 
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