Cyrus 2 Resistors

[Sonusthree]

Hi Geoff,
The Cyrus 2 already had Elnas installed and I recently replaced them with 12,000uF Nichicons as an experiment before getting the PSX recapped. I have heard a few people say that they don't have slit foils as standard either.I was quite happy with the results at the time but it is all relative and I have gained new insight into the sound I am looking for. For some unknown reason I was lacking bass and this is what I focused on in listening tests. I took my eye off the big picture.

I'll try it without the PSX and see what happens.

Best regards,
Martin.

[mannotanumber]

Geoff

Just an update on the original post, I've now replaced the components in the output stage that were blown including the output transistors, the Cyrus is now working fine with the external PSX. So many thanks. The righhand channel (which is the one that was damaged is now substantially clearer than the left - do you think that replacing all the transistor would help to even things out, also I don't seem to have a lot of bass - my speakers have always been laking somewhat in this department, I bought the Cyrus and PSX of e-bay together and they have always sounded the same - even pre repair, Would changing the caps help ? although the unit has been serviced my Cyrus in the past before I bought it. I have no way of knowing what was replaced.

Many thanks again

Dave

[Sonusthree]

Hi,
I'm glad to hear that it's working!! Well done! It gives me hope that I may fix my blown Cyrus One.

Did you only replace one channel's transistors? It's recommended to replace both sets with the same type. It's very interesting that you have more detail with the new ones. Do you prefer the sound? Which transistors did you use?

The Cyrus amps, even with PSX, were always known for their rather forward nature and this is the problem that I had. My speakers have four 8" drivers in large cabinets but the bass was still a little overun by the mid/treble. I assume that you've read the rest of this thread and how I modified my Cyrus 2 and PSX. I ended up with a bit more bass and it was a lot more solid but I lost something else in the process.
I don't want to discourage you from tinkering but do so with open eyes/ears and don't modify without thorough listening tests at every stage. To be fair though, I did go a little overboard on the PSX. Do you have slit foils caps in your C2/PSX or something else? Cyrus' service department told me that they don't replace them because they are stable. I'm not so sure about that so I changed them. I just can't be sure why I have lost some of that detail.

Do you get more bass with the PSX or using the internal supply?

How is your speaker placement? Have you tried them against a wall? It usually helps a bit.

Best regards and happy Easter,
Martin.

[Geoff]

Dave

I'm pleased to hear that you have got your Cyrus 2 working again. The difference in clarity between the channels may well be due to the replacement components you have fitted so it could be a good idea to make the same changes to both channels. In fact, when I contacted Cyrus many years ago the service engineer recommended changing all the output transistors even if only one or two had blown. I didn't do so and didn't notice any difference when the amp was compared with another Cyrus 1 that hadn't had any work done on it.

The lack of bass may be due to capacitor ageing, a lot depends on when your amp was serviced by Cyrus. Again when I contacted Cyrus, I was informed that they replaced all on-board electrolytics as a matter of course whenever an amp went in for service or repair. The prime suspect is the 470uF non-polarised capacitor in the feedback network (C41/42 in your v6). Unfortunately, though most suppliers have a 470uF 6.3V NP in their stock range, I have been unable to find a source in the UK for a quality capacitor to use in this position, eg a Nichicon Muse as originally fitted in one of my Cyrus amps. It is desirable to use a good quality capacitor in this position and the only solution is either to import some suitable capacitors from the States or elsewhere (expensive in small quantities due to handling charges etc) or to use two 1000uF polarised electrolytics back-to-back.

Geoff

[Sonusthree]

I had a similar problem finding the correct part so went for these Black Gates :

http://www.hificollective.co.uk/comp...te_n_type.html

[optimiser]

Hi,

Have just replaced all the faulty output and driver transistors on my early Cyrus 2.

I get sound out both channels so that's fine.

Problem is R110 connected to C61 large resistor gets very hot and have seen it smoking, but not sure what the problem is?
It's the resistor with ceramic washers on the PCB.

The 3.15A fuses have not blown yet.

This amp was previously used with a PSX, so apart from the fuses have I missed anything?

[Sonusthree]

Hi Optimiser,

Which version of the Cyrus 2 do you have? (Does it have a metal or plastic case, a headphone socket and/ or a push or toggle switch?) I'm guessing that it's an early plastic model.

Have you traced that part of the circuit?
Is it a 'bleeder' resistor to discharge the caps?

I only have one early plastic Cyrus and I don't fancy dismantling it again!

Cheers,
Martin.

[optimiser]

It's the plastic case version with headphone socket and push button.

I have been testing the Cyrus 2 through headphones and also with Ruark Talisman 2's for about an hour and it's working great, and the resistor seems to have stopped smoking now.

The resistor is connected to D6 and D8 rectifier diodes.

One of the diodes looks as though it has been replaced as it is darker than the other 3 marked as MR852. Should I replace these diodes as a precaution perhaps?

The amp was serviced by Mission a few years ago and has had all the usual caps replaced.

Does anyone know the original value of R110 which is a power resistor, and measures about 190R but the markings look a bit worn. It looks like brown white brown, so could be 190R ?

[Geoff]

Originally posted by optimiser
Does anyone know the original value of R110 which is a power resistor, and measures about 190R but the markings look a bit worn. It looks like brown white brown, so could be 190R ?

This resistor is 180R. It feeds the 'power on' LED from the junction of D6/D8. The arrangement is similar to that shown on my website for the Cyrus v7 power supply except that a single 180R resistor (R110) is used in place of the two 100R resistors (R119 & R120) that are fitted on the later version.

The current through this resistor, and the LED, is rather high (too high IMO) so it will get warm.

Geoff

[optimiser]

Thanks Geoff.

Ah, ok, so it's just to supply the LED and nothimg to worry about then.

Is there a way of getting more bass out of the Cyrus, or do the later versions with metal case have more bass? or should I think about getting a PSX like I had before. I sold my PSX a few years ago.