I think this qualifies as being insane.

[auralfixaton]

Not so sure it safe to turn it on with those wires not connected!
Maybe someone like Echowars can pipe in here with a bit of information.

 

[phildoc]

Not so sure it safe to turn it on with those wires not connected!
Maybe someone like Echowars can pipe in here with a bit of information.

You might be right. All it did the time I tried it before knowing the wires were cut was blow the fuse. With the wires cut the circuit must be seeing a near short. From what I gather, and its been a while since I've worked with this type of circuit, the only resistance would be the two coils of the transformer and the thermal protection, which should be a short. I'll connect the wires back up and see what happens. Wish me luck.

 

[phildoc]

Well, I reconnected all the wires and it popped the fuse again. Back to the drawing board. Any ideas?



Edit: Well, I tried something that may have been stupid. I cut the same wires that were cut on the channel that appears to be working. It didn't blow the fuse. At this point, I'm thinking that I have a bad transformer. Tomorrow, unless someone has a better idea, I'm going to swap transformers or at least move the transformer for channel A over to channel B. If it doesn't blow the fuse. I at least solved one problem.

 

[Zedhead70]

Insanity is doing the same thing over again expecting the result to be different!

Hi Phildoc, I suggest you rig up a simple test circuit that I use when testing amps that are blowing fuses. It is a globe in series with the mains that, if there is something faulty i.e. shorted in the amp, causes the globe to glow brightly and drop the voltage available to the amp, thus warning you to a potential problem and not blowing fuses every time you turn it on to test.
I am in Australia so the terminology may be slightly different but the principles are the same, I hope I can explain it. I have a couple of incandescent light globes, one 100 Watt the other 200 Watt, depending on the power rating of the amp I'm testing, that I fit into a batten fitting screwed to a timber board (these are the standard ceiling fittings that the light globes screw into). It is wired with a mains plug on one end and the globe in series with the active wire to a standard mains socket on the other end that I can plug the mains lead from the amp (or other unit I'm testing, this works for pretty much any hifi gear and then some) that I'm testing. Please excuse the simple explanation as I don't know how technical you are, it would be much easier to show you but I'm trying to think how to put it into words. At the wall outlet, there is an active (I think it is the wider one over there) connection and a neutral connection. Down here, we have an active (Brown), neutral (Blue) and earth (Green/Yellow). The active is always switched, on the amplifier the main power switch has the mains fuse in series with this line(i.e. in the same wire/line) and switches the active line from the wall outlet. The power switch on the amp sometimes switches the active and neutral but the wire that we want the light globe in series with is the one that has the mains fuse in its circuit. Basically you want to put the globe in circuit with the active wire between the wall outlet and the amp, the neutral wire goes straight from the wall outlet to the amp. I hope that makes sense, I have Lead Poisoning at the moment and it really makes it hard to think straight, as well as an active 7 year old daughter running around in the background, that's my excuse anyway.
What this setup does is basically prevents anything else in the amp blowing up if there is a short. As the globe glows brighter, its resistance increases and it drops the voltage and limits the current going to the amp under test. In your case, what I'd do seeing as you have one good channel, let's keep it that way. I'd try and isolate the transformer secondaries from the bridge rectifier in the crook channel and then power up the amp via the globe. If the globe glows really brightly, it means that the transformer is shorted. If the globe doesn't glow or does so very dimly, you should be able to read the secondary voltages with a meter, I'd imagine 30 to 45 volts AC. I'd keep adding component groups back into the circuit i.e. the bridge rectifier, then filter caps,discharge the filter caps before adding the power amp stages with the output transistors out of circuit. Do this until the globe starts glowing brightly and you'll isolate the faulty components without continually blowing mains fuses and risking further damage. I hope this makes sense, I actually now have a board wired up with a lead to plug into the mains going to the globe batten fitting then going to a switch then a mains socket and also a variac wired up on the same board. If I have done any work on an amp and I'm not sure of it's condition, I always power it up first via the globe it's saved my bacon on many occasions. Regards Craig.

 

[Gibsonian]

In larger amplifiers I advocate the use of prunes in lieu of raisins.

 

[phildoc]

Hi Phildoc, I suggest you rig up a simple test circuit that I use when testing amps that are blowing fuses. It is a globe in series with the mains that, if there is something faulty i.e. shorted in the amp, causes the globe to glow brightly and drop the voltage available to the amp, thus warning you to a potential problem and not blowing fuses every time you turn it on to test.
I am in Australia so the terminology may be slightly different but the principles are the same, I hope I can explain it. I have a couple of incandescent light globes, one 100 Watt the other 200 Watt, depending on the power rating of the amp I'm testing, that I fit into a batten fitting screwed to a timber board (these are the standard ceiling fittings that the light globes screw into). It is wired with a mains plug on one end and the globe in series with the active wire to a standard mains socket on the other end that I can plug the mains lead from the amp (or other unit I'm testing, this works for pretty much any hifi gear and then some) that I'm testing. Please excuse the simple explanation as I don't know how technical you are, it would be much easier to show you but I'm trying to think how to put it into words. At the wall outlet, there is an active (I think it is the wider one over there) connection and a neutral connection. Down here, we have an active (Brown), neutral (Blue) and earth (Green/Yellow). The active is always switched, on the amplifier the main power switch has the mains fuse in series with this line(i.e. in the same wire/line) and switches the active line from the wall outlet. The power switch on the amp sometimes switches the active and neutral but the wire that we want the light globe in series with is the one that has the mains fuse in its circuit. Basically you want to put the globe in circuit with the active wire between the wall outlet and the amp, the neutral wire goes straight from the wall outlet to the amp. I hope that makes sense, I have Lead Poisoning at the moment and it really makes it hard to think straight, as well as an active 7 year old daughter running around in the background, that's my excuse anyway.
What this setup does is basically prevents anything else in the amp blowing up if there is a short. As the globe glows brighter, its resistance increases and it drops the voltage and limits the current going to the amp under test. In your case, what I'd do seeing as you have one good channel, let's keep it that way. I'd try and isolate the transformer secondaries from the bridge rectifier in the crook channel and then power up the amp via the globe. If the globe glows really brightly, it means that the transformer is shorted. If the globe doesn't glow or does so very dimly, you should be able to read the secondary voltages with a meter, I'd imagine 30 to 45 volts AC. I'd keep adding component groups back into the circuit i.e. the bridge rectifier, then filter caps,discharge the filter caps before adding the power amp stages with the output transistors out of circuit. Do this until the globe starts glowing brightly and you'll isolate the faulty components without continually blowing mains fuses and risking further damage. I hope this makes sense, I actually now have a board wired up with a lead to plug into the mains going to the globe batten fitting then going to a switch then a mains socket and also a variac wired up on the same board. If I have done any work on an amp and I'm not sure of it's condition, I always power it up first via the globe it's saved my bacon on many occasions. Regards Craig.

Hey Craig,

I think I pretty much follow what you're saying and its an excellent idea. I think in this case, it pretty has to be a bad transformer. The wires to both rectifier circuits have been cut. From my understanding, that would mean that nothing beyond that could be causing the fuse to be blown. Nothing past the transformer is getting power.

I probably should have know this, but its been 30yrs since I've used any basic electricity. I knew that a coil would look like a short to DC and that you'd get some impedance with AC current, but I wasn't sure if you'd get enough resistance to keep the fuse from blowing with just the transformer. Which is why I cut the same leads on the good channel. Because the fuse didn't blow when I cut the leads. It pretty much has to be the transformer shorting out. The reason I was thinking about swaping them, was to figure out if anything else was faulty. I suppose I should make sure I can I find another transformer before I do that.

Of course I could be full of , lol

Anyway, does anyone know where I can get a replacement transformer for the Citation 16? Would it be possible to get it rewound?

Phil

 

[Zedhead70]

Hi Phil, glad you made sense of it. Have a look at the secondary voltage on the good channel and see if you can match up an after market transformer. Another solution I used recently was to find a transformer from another scrap unit that had a similar power rating, I just looked at the total power consumption figure on the id label on the back of the units and found something pretty close, in this case I had a Kenwood receiver rated at 450Watts or so and used a transformer from a JVC receiver rated at 420 Watts. The difference in secondary voltages was only about 1 or 2 volts if I recall so it worked fine. At least that's a few ideas to go on, or, as you said try and get the original rewound but first see if you can find out if there's any other problems with the crook channel and then look at the viability of doing a rebuild on the unit or putting it aside and looking at some of the other units you have, you never know your luck you may just come across another Citation one day and be able to build one out of two, I have actually done that with a few decent units but it depends on how much space you have and how tolerant your other half is!
Good luck, Craig

 

[phildoc]

Hi Phil, glad you made sense of it. Have a look at the secondary voltage on the good channel and see if you can match up an after market transformer. Another solution I used recently was to find a transformer from another scrap unit that had a similar power rating, I just looked at the total power consumption figure on the id label on the back of the units and found something pretty close, in this case I had a Kenwood receiver rated at 450Watts or so and used a transformer from a JVC receiver rated at 420 Watts. The difference in secondary voltages was only about 1 or 2 volts if I recall so it worked fine. At least that's a few ideas to go on, or, as you said try and get the original rewound but first see if you can find out if there's any other problems with the crook channel and then look at the viability of doing a rebuild on the unit or putting it aside and looking at some of the other units you have, you never know your luck you may just come across another Citation one day and be able to build one out of two, I have actually done that with a few decent units but it depends on how much space you have and how tolerant your other half is!
Good luck, Craig

Hey Craig,

All good ideas. As you can see I have a lot of cobwebs to dust off. As you can see from the circuit diagram above. The 60v goes to the power transistors and the 12v goes to the leds. Might be hard to find a transformer with that configuration.

Either way, I only have a DVM. With that in mind what measurements would you take. Power on, current/voltage across each seconday? Do I need to disconnect anything? Sorry for the nube questions, but its been a very long time.

Thanks for all your help,

Phil

 

[Zedhead70]

Hi Phil, glad to help where/when I can.To test the secondary of the transformer, find out where the bridge rectifier or diodes are and measure the AC voltages there. You should have around 40 to 50 volts AC on both AC inputs to the bridge rectifier referenced to ground, so connect one lead of the meter to ground/earth/chassis of the amp and the other to either of the AC inputs to the diodes. Looking at the Citation circuit you attached these points are numbered 10 and 12. The voltages should be virtually the same as each other, i.e. 42 + 42 Volts, 46 + 46 Volts etc. Finding a transformer with that configuration won't be as hard as you think, there are plenty of after market ones that have dual secondary tappings with a low auxiliary tapping of 9 - 12 volts and then a main of 35 to 55 volts centre tapped. Another is to use 2 transformers, a small one for the twelve volts a larger one for the other etc. As far as power rating is concerned, the biggest you can fit in the space but off the top of my head at least a 200VA rating, but check on that. As I said previously if you look at the total power consumption on the id label and find an amp with a similar power rating, you should be fine. Have a look at toroidal transformers in RS Components, it's quite possible they may have something. If the lower voltage secondary, the 12 volts, only feeds the lamps, and you can only find a tranny with 9 volts or 15 volts, then just change the lamps to suit, I did that with the Kenwood JVC swap-over. See how you go with that, Regards Craig.

 

[phildoc]

Hi Phil, glad to help where/when I can.To test the secondary of the transformer, find out where the bridge rectifier or diodes are and measure the AC voltages there. You should have around 40 to 50 volts AC on both AC inputs to the bridge rectifier referenced to ground, so connect one lead of the meter to ground/earth/chassis of the amp and the other to either of the AC inputs to the diodes. Looking at the Citation circuit you attached these points are numbered 10 and 12. The voltages should be virtually the same as each other, i.e. 42 + 42 Volts, 46 + 46 Volts etc. Finding a transformer with that configuration won't be as hard as you think, there are plenty of after market ones that have dual secondary tappings with a low auxiliary tapping of 9 - 12 volts and then a main of 35 to 55 volts centre tapped. Another is to use 2 transformers, a small one for the twelve volts a larger one for the other etc. As far as power rating is concerned, the biggest you can fit in the space but off the top of my head at least a 200VA rating, but check on that. As I said previously if you look at the total power consumption on the id label and find an amp with a similar power rating, you should be fine. Have a look at toroidal transformers in RS Components, it's quite possible they may have something. If the lower voltage secondary, the 12 volts, only feeds the lamps, and you can only find a tranny with 9 volts or 15 volts, then just change the lamps to suit, I did that with the Kenwood JVC swap-over. See how you go with that, Regards Craig.

Hey Craig,

Wow, that should more than help get me going. I'll get the measurements as soon as I can and I'll check out RS for the toroidal. Hopefully, I'll have this beast up and running soon. Thanks so much again for your help.

Phil

 

[phildoc]

Just to let you know it measured 50v AC at one rectifier and 12v AC at the other. I probably should have tried this before, but I hooked up one of the 9090s to the good channel and was able to get a radio station on the speaker. That mean the L channel is definately good on the 16 and the preamp is good on the 9090. Thanks again.

Phil

 

[JoeESP9]

Yesterday the bug struck me and before I knew it I had bought 6 pieces of gear. All of it not working of course. The Nakamichi tape deck was suppose to work, but it ended up needing attention as well. Here's the list.

1. 2 Sansui 9090
2. HK Citation 16
3. Crown DC-300a mkII
4. Crown DC-150a
5. Nakamichi BX-125

The Nakamichi fired up but the sound was all distorted. A head cleaning helped, but it was going to need a new belt. Funny thing is when I opened it up. There was a new belt inside. Along with a raisin, lol. Changed the belt and it sounds beautiful.

One Sansui lights up and can tune stations, but not sound. The other goes into protect mode.

The Citation blows a fuse on one channel. The other channel works fine.

The 300a also has one good and one bad channel. I haven't tried the 150a.



I'm going to start with the Sansui's. Give them both a good cleaning and then go from there. I will say without a doubt. I'm in way over my head, lol.

If you need a case for the DC300 I have one you can have for free. PM me if you can use it.