After reading this thread: http://www.diyaudio.com/forums/solid-state/199400-repair-help-requested-creek-4240se.html I gave it a shot.
Well it didn't work after replacing all the transistors. One of the bridge diodes, or maybe the small cap next to it, started to smoke. The transformer heated up too. This happened even after I pulled the internal fuses between the power supply and the amp section. In the schematic it shows the fuses between the tranny and the bridge, but in reality the fuses are after the big caps.
I'm calling it a day for now. The only thought I have is to pull the transformer output leads off the circuit board and then see, and read the voltage there. That doesn't tell me much except that the transformer works. Maybe I'll replace all the PS section since it isn't that many parts. The electrolytics were replacements that I tried as an attempt in the past to fix this amp, so they haven't ever been in use.
Any other ideas out there?
Well it didn't work after replacing all the transistors. One of the bridge diodes, or maybe the small cap next to it, started to smoke. The transformer heated up too. This happened even after I pulled the internal fuses between the power supply and the amp section. In the schematic it shows the fuses between the tranny and the bridge, but in reality the fuses are after the big caps.
I'm calling it a day for now. The only thought I have is to pull the transformer output leads off the circuit board and then see, and read the voltage there. That doesn't tell me much except that the transformer works. Maybe I'll replace all the PS section since it isn't that many parts. The electrolytics were replacements that I tried as an attempt in the past to fix this amp, so they haven't ever been in use.
Any other ideas out there?
I was going to do that. The transistors I tested after I pulled them all came up bad, so something really fried this thing. And just to check I was doing it correctly I tested a few new transistors and they all came up good.
I'm going to check the output from the transformer too, it should be 25vac.
And if all this fails, I'm thinking I'll just wire in a 3116 or something like it and use the switches, jacks etc... Or even a better idea, finally put my Aikido into a real box. I'm pretty sure I can isolate the pre-amp traces from the power section on the board. And the funny thing is that the Creek phono-pre add-on that I had installed in the 4240 ended up as the phono section of my Aikido. I could put it back into its original slot.
I'm going to check the output from the transformer too, it should be 25vac.
And if all this fails, I'm thinking I'll just wire in a 3116 or something like it and use the switches, jacks etc... Or even a better idea, finally put my Aikido into a real box. I'm pretty sure I can isolate the pre-amp traces from the power section on the board. And the funny thing is that the Creek phono-pre add-on that I had installed in the 4240 ended up as the phono section of my Aikido. I could put it back into its original slot.
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So what I've found today...
First, I pulled the diodes and checked them. 3 of them seem to be good, with resistance/open in the proper direction and the diode check showing .4v to .5v drop in voltage. My understanding is that meters can't check to the full .7v that they drop in use. The fourth one cracked when I pulled it, and this is the one that smoked yesterday, so I can't check it.
The transformer is putting out 26vac from the leads, which is only slightly above the 25vac spec. I assume that's OK, and could just be my main voltage being high.
I also pulled the electrolytics, the 6800uf ones, and my meter won't read these high values, although quite honestly I'm not sure if I'm doing it right anyway. I have some smaller value caps that I can check to see if I'm doing it right. And just to be clear, the negative marking on the cap should go to ground, correct, and the positive goes to the + on the board? I know that seems obvious but I just have to ask.
So at this point I'm thinking that either the one diode was bad, or that the one diode became bad from something downstream. I don't have 3amp diodes on hand so I will need to order some more. Where is the RatShack when you need them? They were always good for a part in a pinch, although I'd be the first to say I couldn't see how they stayed in business the last 5-10 years.
First, I pulled the diodes and checked them. 3 of them seem to be good, with resistance/open in the proper direction and the diode check showing .4v to .5v drop in voltage. My understanding is that meters can't check to the full .7v that they drop in use. The fourth one cracked when I pulled it, and this is the one that smoked yesterday, so I can't check it.
The transformer is putting out 26vac from the leads, which is only slightly above the 25vac spec. I assume that's OK, and could just be my main voltage being high.
I also pulled the electrolytics, the 6800uf ones, and my meter won't read these high values, although quite honestly I'm not sure if I'm doing it right anyway. I have some smaller value caps that I can check to see if I'm doing it right. And just to be clear, the negative marking on the cap should go to ground, correct, and the positive goes to the + on the board? I know that seems obvious but I just have to ask.
So at this point I'm thinking that either the one diode was bad, or that the one diode became bad from something downstream. I don't have 3amp diodes on hand so I will need to order some more. Where is the RatShack when you need them? They were always good for a part in a pinch, although I'd be the first to say I couldn't see how they stayed in business the last 5-10 years.
So here is another update, over a month later.
I ordered diodes, the 100n caps, both ceramic and film as specified, and the 6800uf electrolytics. I re-installed all of it, connected up the transformer outputs, reconnected the on/off LED (wire came off the board), looked it all over with a magnifying glass, and tried the amp without the fuses that connect the PS to the circuit. Everything was OK.
I then put the fuses in, plugged in my iPhone as a source on the CD input, plugged my son's speakers (only ones with a banana at the amp end) and gave it a try. Music! but only one channel, and then the amp hums loudly too.
So what else could I try? PS is good, since I did get one channel, so it must be something on the other channel. I tried swapping inputs, and the speakers, just to check that all that is working, and it wasn't, but I figured that part out pretty quickly. The connection in my iPhone isn't solid. (Aren't there two similarly sized plugs that aren't quite a good fit with each other?). But recognizing that I could still only ever get music out of the left channel.
What bothers me is that the fuse does NOT blow. If it is drawing too much current from a shorted part I would think it would blow. In the brief time I've had it on it hasn't gotten anything hot, whereas with the bad diode the transformer got hot in a hurry.
One thing I didn't do but I bought the parts was to replace the zener diodes. I could try this.
The good news anyway is that I bought extras of everything when I ordered. If I have to re-assemble the entire channel I have enough I think.
I ordered diodes, the 100n caps, both ceramic and film as specified, and the 6800uf electrolytics. I re-installed all of it, connected up the transformer outputs, reconnected the on/off LED (wire came off the board), looked it all over with a magnifying glass, and tried the amp without the fuses that connect the PS to the circuit. Everything was OK.
I then put the fuses in, plugged in my iPhone as a source on the CD input, plugged my son's speakers (only ones with a banana at the amp end) and gave it a try. Music! but only one channel, and then the amp hums loudly too.
So what else could I try? PS is good, since I did get one channel, so it must be something on the other channel. I tried swapping inputs, and the speakers, just to check that all that is working, and it wasn't, but I figured that part out pretty quickly. The connection in my iPhone isn't solid. (Aren't there two similarly sized plugs that aren't quite a good fit with each other?). But recognizing that I could still only ever get music out of the left channel.
What bothers me is that the fuse does NOT blow. If it is drawing too much current from a shorted part I would think it would blow. In the brief time I've had it on it hasn't gotten anything hot, whereas with the bad diode the transformer got hot in a hurry.
One thing I didn't do but I bought the parts was to replace the zener diodes. I could try this.
The good news anyway is that I bought extras of everything when I ordered. If I have to re-assemble the entire channel I have enough I think.
I just thought of something that hadn't occurred to me before. I was looking at the schematic focusing on the sections with the ICs since I hadn't really touched those. I then went to the amp sitting behind me, still open from a few weeks ago. I turned the balance control when it struck me that I didn't check if it was centered when I first tested it out!
I'll have to give it another try now, but maybe later today as it requires moving things around to get back to my test speakers.
At least I can limit this to one side, since the other is working. Maybe I blew yet another transistor.
I'll have to give it another try now, but maybe later today as it requires moving things around to get back to my test speakers.
At least I can limit this to one side, since the other is working. Maybe I blew yet another transistor.
Rather rather than just keep building a bigger pile of dead parts, find if there are shorts or other destructive faults without compounding the damage by using a light bulb tester. It's dead simple, fail safe and you can make it from electrical fittings or even an old table lamp, line socket and 60W globe.
http://www.diyaudio.com/forums/power-supplies/167579-light-bulb-tester.html
http://www.diyaudio.com/forums/power-supplies/167579-light-bulb-tester.html
That sounds like a good idea, except I've barely had time to work on this thing. I do have a variac though, so maybe the next time I try this I'll put it on that first.
The power supply does seem to be stable, and I do get one channel, so probably I have one component on the other channel that got fried, either when it went out the first time, or even after I replaced everything. If I can't get this to work it is no big deal. It hasn't worked in years and I was being pressured to just toss it by the wife. I just thought that the chassis would be worth saving, with the connections too, for my Aikido pre-amp. Before I did that I thought I'd try restoring it based on the other thread.
The power supply does seem to be stable, and I do get one channel, so probably I have one component on the other channel that got fried, either when it went out the first time, or even after I replaced everything. If I can't get this to work it is no big deal. It hasn't worked in years and I was being pressured to just toss it by the wife. I just thought that the chassis would be worth saving, with the connections too, for my Aikido pre-amp. Before I did that I thought I'd try restoring it based on the other thread.
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