My longtime favorite tube amp and one of my first builds is my SSE that I built in 2006? With the cooler weather setting in, I swapped out my summer Class-D amp for the SSE and it's been getting some heavy use when I've been working from home.
Yesterday I flipped the switch on the SSE and after a few moments the chassis gave off a strong hum and then popped it's 4A fuse. No smoke, just some short somewhere. So it's troubleshooting time!
Tubes and speakers check out OK. I'm guessing I'll check the transformers for shorts, and if nothing found there I'll have to remove the board and trace it out. I should have all the spares I need. Let the adventure begin...
Yesterday I flipped the switch on the SSE and after a few moments the chassis gave off a strong hum and then popped it's 4A fuse. No smoke, just some short somewhere. So it's troubleshooting time!
Tubes and speakers check out OK. I'm guessing I'll check the transformers for shorts, and if nothing found there I'll have to remove the board and trace it out. I should have all the spares I need. Let the adventure begin...
Good tips everyone. I noticed that the RCA input switcher wasn't playing nice and I wonder if it was doing bad things. Possible short on the input. 100% Recoton (Radio Shack) quality there.
I'll pull the solid state rectifiers since I don't use them. Also I noticed the thermistor on the mains is cracked up, but I would expect that to close the circuit.
I have a midterm paper due so I won't be able to get too deep into this real soon.
Cheers!
I'll pull the solid state rectifiers since I don't use them. Also I noticed the thermistor on the mains is cracked up, but I would expect that to close the circuit.
I have a midterm paper due so I won't be able to get too deep into this real soon.
Cheers!
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I'm suppose to be working on a 25 paper but instead I'm overwhelmingly inspired to troubleshoot my SSE. 
It's drawing 130w at the wall, which is expected and good.
B+ 357v
OPT screen tap 350v
Did a bit of tube rolling, and the hum became less so, but still substantial. The tube that was in there was super sensitive to vibration so that wasn't helping a ton.
So I'm under the impression all the big iron is OK. I'm inclined to replace the electrolytics, partly because my test equipment is limited to a multimeter and a kill-a-watt.
I just realized my only working tube amp is my firefly guitar amp. My other 3 nice audio amps are in need troubleshooting. LOL! Of course it will get warm outside and I'll only want to be outside with the family.
It's drawing 130w at the wall, which is expected and good.
B+ 357v
OPT screen tap 350v
Did a bit of tube rolling, and the hum became less so, but still substantial. The tube that was in there was super sensitive to vibration so that wasn't helping a ton.
So I'm under the impression all the big iron is OK. I'm inclined to replace the electrolytics, partly because my test equipment is limited to a multimeter and a kill-a-watt.
I just realized my only working tube amp is my firefly guitar amp. My other 3 nice audio amps are in need troubleshooting. LOL! Of course it will get warm outside and I'll only want to be outside with the family.
Some progress today. I removed the choke and replaced it with a 330 ohm 5w resistor because that is what I had, and also removed the aux capacitor. Very strong 60hz hum! Wow. I'm suspicious of the c1 capacitor. I have a 47uf 450v which should be OK since. the B+ before the resistor is about 370v.
Considering the age it is advisable to not do a slap-dash thingie but replace all serviceable parts i.e. all electrolytic caps for new good quality parts. To do things good so to speak. Working on stuff 5 times does cost eh.. 5 times more time. Time you could use to write papers.
To reuse stuff one already has (and that maybe also be old/dried out) may seem good practice.. Ah well, do as you please.
To reuse stuff one already has (and that maybe also be old/dried out) may seem good practice.. Ah well, do as you please.
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I have plenty of the SSE boards, but you may not need to completely start over there are plenty old SSE's out there working just fine. Let's try to fix this one first.
I don't remember what tube set and power transformer you used in your build, but most SSE's run at over 400 volts of B+, usually about 430 volts.
You say the R24 looks toasty. Does R14 look the same? You might have a dead IXYS 10M45 chip. This will cause low gain in that channel and too much current flow through that half of the 12AT7. Measure the voltage on either end of R24 there should be about 100 volts difference. If there is considerably more voltage across R24 and no voltage drop across the 10M45 the chip is dead. The 12AT7 may be damaged from the excessive current.
Which power transformer are you using, and is it still vibrating? If so, remove the rectifier tube and see if it still vibrates. If so the transformer itself may have a shorted winding. This is not common. Replace the rectifier and measure the voltage across the cathode resistors (R17 and R27). They should be relatively equal. One or both output tubes could have become gassy and are drawing too much current. This is unfortunately quite common with current production tubes that have some considerable run time.
There is just a light bit of browning on the pad on one side of R24 and some minor browning on the resistor itself. The R14 is less so. The gain seems OK. But in any case I think I have a stash of the 10M45 somewhere.
I've been using a Hammond 373BX which is 700 vct, a 193H choke, and Edcor GXSE-10-8-5k for output. I'm using a set of old International Servicemaster KT88's, and I've also tested with some crusty G.E.C. KT88 with no change. I did swap out the 5AR4 with no change. I'll have to check the power transformer again where I was planning to sell it, and I don't want to sell a dud. It only vibrates minimally, but the choke was really vibrating.
I pulled off C1 (Panasonic UP series 47uF 500v) , and it looks OK. I tested it with a 3.2v battery and it seemed like the capacitor is shorted where all the voltage went right through it. I recall capacitors aren't supposed to do that.
Board is ordered, but I'm Ok with troubleshooting too.
I've been using a Hammond 373BX which is 700 vct, a 193H choke, and Edcor GXSE-10-8-5k for output. I'm using a set of old International Servicemaster KT88's, and I've also tested with some crusty G.E.C. KT88 with no change. I did swap out the 5AR4 with no change. I'll have to check the power transformer again where I was planning to sell it, and I don't want to sell a dud. It only vibrates minimally, but the choke was really vibrating.
I pulled off C1 (Panasonic UP series 47uF 500v) , and it looks OK. I tested it with a 3.2v battery and it seemed like the capacitor is shorted where all the voltage went right through it. I recall capacitors aren't supposed to do that.
Board is ordered, but I'm Ok with troubleshooting too.
I thought about this some more and came up with another possibility. You stated that you have a 60 Hz buzz. A typical power supply problem like a bad cap will produce a 120 Hz buzz due to the full wave rectifier. A 60 Hz buzz indicates that your power supply is missing half the wave. This also causes transformer and choke buzz. Measure the continuity of both halves of the HV secondary and trace that continuity to the pins of the rectifier tube. You should have an ohmmeter reading of less than a few hundred ohms from pins 4 and 6 on the 5AR4 socket to ground and both readings should be close to each other. The transformer itself, the screw connectors, and the tube socket are likely suspects here. Solder joints can become brittle in 15 years too. Try reheating them.
I was thinking the same thing about the have-wave thing. Both sides of the HV secondary have the same resistance and good continuity. I'm feeling good about the power transformer, but I've ordered a 274BX anyway for the extra volts.
I've disassembled the amp so bench testing is a bit difficult now. I'm going to take a drunken man approach for repair and just blindly replace some parts.
The Plan:
Replace the CCSs, and some of the electrolytics, and the thermistor on the mains switch. I may replace R24, R14 just for good measure.
I've disassembled the amp so bench testing is a bit difficult now. I'm going to take a drunken man approach for repair and just blindly replace some parts.
The Plan:
Replace the CCSs, and some of the electrolytics, and the thermistor on the mains switch. I may replace R24, R14 just for good measure.
Hi everyone. After poking at a lot of rework, I've got the SSE back up and running! Hum is gone.
The hardest part was trying to figure out all my terrible wiring that is external to the board, which I expected. So I only wanted to repair it once, rather than experiment and root-cause it. I replaced the IXYS 10M45, bias resistors, power supply electrolytics and the power transformer (now a 274BX). I put the nice C11,C21 caps back in too. A not-so-great looking thermistor got removed. I also changed out the 12AT7. That's all.
I couldn't find the 560 ohm bias resistors I used to have in, so I used something like 680 ohm because I had 'em. Seems good enough, and I imagine the reduced dissipation might help tube life.
Sounds great! The 274BX has some mechanical noise, but it's not noticeable from a distance, or with the volume cranked up. Now I've got a sick EAR509 to repair, and a pair of all-original McIntosh MC75s to bring back to life. At least I've got one to listen to now.
The hardest part was trying to figure out all my terrible wiring that is external to the board, which I expected. So I only wanted to repair it once, rather than experiment and root-cause it. I replaced the IXYS 10M45, bias resistors, power supply electrolytics and the power transformer (now a 274BX). I put the nice C11,C21 caps back in too. A not-so-great looking thermistor got removed. I also changed out the 12AT7. That's all.
I couldn't find the 560 ohm bias resistors I used to have in, so I used something like 680 ohm because I had 'em. Seems good enough, and I imagine the reduced dissipation might help tube life.
Sounds great! The 274BX has some mechanical noise, but it's not noticeable from a distance, or with the volume cranked up. Now I've got a sick EAR509 to repair, and a pair of all-original McIntosh MC75s to bring back to life. At least I've got one to listen to now.