ART150 not switching on

[ELM]

Hello CJOs,

I would like to seek your advice on my ART150.

When I turned on the ART150 tonight, the indication light around the power on switch lit for 1 second and then went off. Afterwards it no longer power on. The wall sockets were checked and confirmed in a normal state. I also did the power on procedure for the system as I normally do, i.e. wait until the ET-5 power indication flashing complete to turn on the power amp.

One thing that may be considered relieving is that there was not any sound coming out from the speakers during the ART 150 light out - hopefully suggesting that it has nothing to do with an internal short circuit or parts failure.

The problem seems to be related to the mains fuse burnt. Notwithstanding the inference, it would be great if I could get insight from this group.

And if it was really related to the mains fuse, is there any sources of instruction which I could refer to replacing the fuse myself? CJ did supply a few spare fuses when they shipped out the amplifier. However there was no mention on the user manual for how to diy the replacement.

I appreciate your advice.

Best regards
ELM

[ELM]

Sorry for the typo in my last message. For suspected fuse burnt, I actually meant fuse blown instead.

[admin]

Sorry to hear about this but replacing the main fuse is luckily very easy as it is right on the back with a screw release.

You can see it on the right and left side of this picture:

This is what the manual says:

The ART 150 Amplifier power transformer is protected by a fuse
on the ac power line (F5, located in a compartment in the ac line- cord receptacle mounted on the back of the amplifier), and by four
separate internal fuses on the secondary circuits of the transformer
(F1 – F4) located on the bottom of the pc board. A failure of any of
these fuses is a symptom of a more serious problem, and a
competent service technician should be consulted. In no event
should fuses be replaced with a value or type different than that
originally supplied. The correct fuse values and types are:
F5: 5x20mm 12 amp T-type if configured for 100 or 120V:
5x20mm 6.3 amp T-type if configured for 220 or 240V.
F4: 5x20mm 3.15 amp T-type
F1, F2, and F3: 5x20mm 200ma T-type

The one you want to look at first is the F5 fuse, the one on the back.

Now with that said, the question is why it blew. I would check the tubes before doing anything else because it may blow the fuse again with the next startup. If you don't see damage and change the blown fuse, restart the unit, watch carefully for any light flicker in the tubes. I would do this in a low light room and again, you have to stair at it carefully to not miss it. If you don't see anything, that doesn't mean the tubes are good and you may need to get your tubes tested.

Also, if things are not working right, don't forget to check all the other fuses in the unit. The cover needs to be removed for these.

Good luck and keep us updated.

[ELM]

Thank you Admin for the information. Very helpful indeed.

Will go ahead with F5 replacement first. I am with you that the blown fuse could suggest some issues behind the scene. Tube failure can be the likely culprit. What baffled me is that with my simplistic understanding a tube will need some amount of time to heat up and function. If this holds true, theoretically a failed tube will take a few seconds to a minute following it lights up to cast its ill effects on the amp. But in my case, the ART 150 power was simply gone in just 1 second after switched on.

I will start with the fuse replacement for F5 position, hopefully not having to touch on F1 to F4 where technicality fails me. I may also need to first place order for the fuse from after market. If memory serves those spare fuses coming along from CJ are meant for the plate fuse KTK-1, not the 5x20mm size for F1 to F5. The ART 150 packing box sits in the garage only accessible tomorrow to confirm size of the fuse.

Thanks
ELM

[admin]

Nope, disagree on how quickly it can blow after startup. I had my tube blow on my ART amp. Changed the fuse to try and find which tube (on the first blow fuse I saw the flash from across the room but not able to identify which tube it was with the initial blow as I was obviously not expecting it) and it flashed almost immediately again. This time I was sitting right in front of it so I could identify which was the bad tube.

You can test the fuse easily with either looking at it or with a continuity meter if you can't see obvious signs of it being blown.

You can order from CJ directly (always a sure choice) or you can try to find the same fuse from a reputable online dealer. The fuse itself will tell you what are its specs.

[ELM]

Thanks Admin again for your further advice. I will bear that in mind.

At least the good thing is I have got a spare set KT150 x 4 for the amp. It was bought in early 2022 when tube prices had not gone crazy yet.

Supplier for spare fuse also identified. The make is SIBA. Never heard of this company before but found that it is a Deutsch company who claims their fuse products all made in Germany. I will give it a try. Some say Bussman nowadays have their fuse made in China. The audiophile grade fuse is less than my cup of tea, not to mention the dearly price.

I will report back on the progress in due course.

Thanks
ELM

[ELM]

Report back the trouble shoot outcome.

The F5 fuse housed under the mains receptacle actually came with two 6.3A fuses. They were meant to protect the power transformer. I opened the casing and found one of the fuses was blown. Replaced both with the SIBA fuses.

I did not run test with the used KT150s. Instead a new set of quad was plugged in along with the replaced fuses. Switched on the amp and problem gone.

At the end I was still not sure whether the fuse blown was associated with a faulty power tube or simply power surge. I would speculate that because of the cold wet weather these days, there was a fair amount of damp air and high humility inside the liner drywall. What made the humid situation worse is that the wall that holds my mains socket for the system has the opposite side outside the house bearing the full weather conditions. The damp air around the socket may cause electric short when the high power amp drew a large amount of current from the mains while the low power consumption equipment remained unaffected. Just my layman guessing.

Anyway I will send the old tubes to test and will keep as spare if they still hold a certain life span.

Meanwhile music flowing again in the room. Happy ending. Cheers

[admin]

Glad it turned out well and a simple new fuse is all what was needed.

[microstrip]

A faulty tube would probably blow the B+ fuse first - they are ultra fast type, to protect the output transformers, and in many cases the cathode resistors.

IMO humidity should not be an issue - house breakers such as the RCCB ( Residual Current Circuit Breaker) would probably have switched mains off in such conditions. However I have found that sometimes pulsing the switch hesitantly or slowly, in a way it creates an instant transient break and switch condition in equipment fitted with high power mains supply transformers can blow the anti-surge type mains fuse of power amplifiers.

BTW, I am not sure if it is the case of the ART150, but sometimes the fuse holders carry two fuses - one is effective in the circuit and the other is just a spare. Manufacturers know that your problem can easily happen!

SIBA fuses are known to be of good quality, but we have to select the proper type of fuse - they have several types with different breaking conditions and fuse time.

[ELM]

Thank you for the insight. It's been helpful.

All are good to know especially the thing about pulsing the switch hesitantly. It was likely the case in point. I remember when I turned on the amp that night, something crossed my mind resulted in a fraction of a second of hesitation that is unlike the usual 'clean shot' pushing the power on button. I had ever wondered if this could be the culprit yet technical knowhow failed me to back my thinking. I think your explanation hit the point.

And I never thought of one of the fuses was there as spare! Again good to realise that.

Cheers

[Big Dog RJ]

That's great news mate, well done.

The fuses are there to protect most things in the unit (trannies, output tubes etc ) but power surges can be an issue. Nothing we can do about that, especially during electrical storms... the best mode of protection is not to power on the system at all!

Nice one on the SIBA fuses, seem to be top quality. Must look into these. Regarding your spare KT150 tubes, they should be pretty good to go for a while, even though a fuse went out. It wasn't the large plate fuse (ceramic type KTK) so most probably your tubes are fine. Nonetheless, since you're getting them tested, that's an excellent way to know then just keep the good ones.
Also, CJ generally doesn't maximise on their current draw with Output tubes in these classic tube circuits. So, most of the time they're just cruising along... which extends tube life much longer than ordinary tube gear. It's quite a remarkable thing they do with this design, so you'll enjoy a lot of hours!

It's those small signal tubes that aren't very reliable, it just takes a while to find the right batch, which can last for years! I've had quite a number of 6922 failures within few months, and others have operated well over 6yrs with no issues. So very inconsistent.

Once you've found a good reliable batch, just stick with that set and sit back and enjoy those finest tunes! Don't bother with tube rolling, especially in ART series amplifiers, they're already at its highest level of performance with Sonic finesse! Nothing further to add.

Woof! RJ

[ELM]

Thanks mate. All well said.

Yes the SIBA fuses are worth checking out. I got mine here in the UK that were made in Germany. You can see if you could find similar from your local suppliers down under.

As for the small tubes, I am with you. My ART 150 had two out of three stock 6922 turned faulty in the first 10 hours of listening. CJ sent me another batch and again two failed which means a 67% defect rate for that batch of tubes.

Other than that I am happy with the amp for the punch it can deliver - as I listen to orchestral music mostly.

Cheers ELM