Well folks I sure had a huge scare.
I've been enjoying my Krell pre so much that I've been procrastinated working on it. Yesterday I turned it and the rest of my system on as usual, and right when my amps' relays clicked there was a massive thump in the speakers and both amps immediately went into protection.
As you recall, my pre is powered by a new Siglent SPD3303X-E bench PSU until its own PSU is recreated.
Long story short, CH 1 of the Siglent died. Instead of getting +21V / -21V the pre was getting +21V / 0V, therefore sending 10.5V DC to the output - and to my amps' input. Explaining the deafening thump.
I tried resetting the Siglent and reflashing the firmware but it didn't help. The display shows the correct settings. When I turn on CH 2 I hear the relay clicking, but I don't hear anything on CH 1.
I'll take a look at the service manual in case I'm missing something obvious, but if not it's under warranty and I'll deal with it Monday.
I've been enjoying my Krell pre so much that I've been procrastinated working on it. Yesterday I turned it and the rest of my system on as usual, and right when my amps' relays clicked there was a massive thump in the speakers and both amps immediately went into protection.
As you recall, my pre is powered by a new Siglent SPD3303X-E bench PSU until its own PSU is recreated.
Long story short, CH 1 of the Siglent died. Instead of getting +21V / -21V the pre was getting +21V / 0V, therefore sending 10.5V DC to the output - and to my amps' input. Explaining the deafening thump.
I tried resetting the Siglent and reflashing the firmware but it didn't help. The display shows the correct settings. When I turn on CH 2 I hear the relay clicking, but I don't hear anything on CH 1.
I'll take a look at the service manual in case I'm missing something obvious, but if not it's under warranty and I'll deal with it Monday.
Wow, didn't you just get the new P/S? Hope warranty covers shipping, it should. Linear supplies are beasts. My similar rigol I think is around 25lbs.
If you have not already, try disconnecting the load in case the it is triggering over current protect. You may have set it, or possibly the krell developed a short.
If you have not already, try disconnecting the load in case the it is triggering over current protect. You may have set it, or possibly the krell developed a short.
@mikeAtx
That PSU s barely 2 months old.
I disconnected the load, turned the PSU off and pulled the plug in an attempt to reset it but that didn't make any difference.
I checked OCP and it's set to 3.5A both channels, much higher than the 1.6A I programmed in.
I'm afraid there's something wrong with it. Hopefully Siglent are pretty good with service.
That PSU s barely 2 months old.
I disconnected the load, turned the PSU off and pulled the plug in an attempt to reset it but that didn't make any difference.
I checked OCP and it's set to 3.5A both channels, much higher than the 1.6A I programmed in.
I'm afraid there's something wrong with it. Hopefully Siglent are pretty good with service.
Well in a way, maybe good. Siglent will likely cover shipping and maybe just send a new one since so new. You may have gotten a bad apple, and fortunately discovered early. Much better than if you fired it up, verified good, and then not used for 8 months only to discover a problem. Warranty might not be as generous after 8 months.
You know what? That is a very good point. I have actually bought a product knowing that I would be using it in the future only to find it was crap or defective. Worst case was small, hand sized saw made by Dremel. Great idea, horrible execution. They quickly quit making them, but it was too late for me.
Yes, yes indeed!
That's the ideal scenario... Fingers crossed
It's the first Siglent instrument I own. Kinda surprised by the early failure as the brand appears to be pretty well regarded. Maybe this particular unit happens to be a lemon.
This post is about fixing a failed ALCO TT41 series toggle switch.
If you recall, during testing I found an pair of pins that were open when they were supposed to be closed. This switch is located on the main board in the phono stage of my Krell pre. It lets the user select between MC and MM cartridge input.
I measured it in-circuit, but the culprit had to be the switch itself. Which, I quickly found, is obsolete and near-unobtainium. There are a few NOS ones floating around, asking for $40 - $50.
Meanwhile a guy was selling a different version of the same switch on eBay (with right angle pins) for $3.75 a piece. So I bought two to use as donors. Here is the OEM switch (left) next to the eBay one (right):
The pitch of the angled-pin rows is only half that of the straight pin rows, so I couldn't just drop in the eBay switch although there would have been enough real estate to do that. The only way was to open up the switches and swap innards. Here is what's in them:
I was expecting springs to jump in my face and get lost but there were no springs.
The four brass crossy things are teeter-totters. The source pin contacts (the center ones) are higher than the two on either side of them, so the brass crosses pivot on them. The plastic sled (center) rocks the brass crosses the opposite way as it moves from one end to the other when the lever (right) is actuated.
It's really super simple. How can something this simple go bad? Well, here's what the base of the OEM switch looked like on disassembly:
You can see that greenish fuzz on the top right side. The problem was pretty obvious:
The plating was peeling off the steel saddle and, presumably, reacting with the brass contacts and forming the green fuzzy residue through some sort of chemical reaction. I cleaned up the base using vast amounts of CRC contact cleaner followed by Deoxit D5, then I started with reassembly. The new switch essentially consists of all the eBay switch's parts, with only the base of the original switch being retained. Here is the finished product:
I used a bit of Caig contact grease on reassembly, and the action feels better than the factory switches'. Parallel-grip pliers are a must to re-form the steel saddle and do this job cleanly.
I was pretty happy with the outcome, until I realized my new switch was quite a bit taller than the old one:
It is actually taller than anything else on the main board, but luckily, according to my measurements there will be one whole millimeter left between the top of the switch lever and the case.
Hopefully this will help someone who's having to deal with those ALCO switches 🙂
If you recall, during testing I found an pair of pins that were open when they were supposed to be closed. This switch is located on the main board in the phono stage of my Krell pre. It lets the user select between MC and MM cartridge input.
I measured it in-circuit, but the culprit had to be the switch itself. Which, I quickly found, is obsolete and near-unobtainium. There are a few NOS ones floating around, asking for $40 - $50.
Meanwhile a guy was selling a different version of the same switch on eBay (with right angle pins) for $3.75 a piece. So I bought two to use as donors. Here is the OEM switch (left) next to the eBay one (right):
The pitch of the angled-pin rows is only half that of the straight pin rows, so I couldn't just drop in the eBay switch although there would have been enough real estate to do that. The only way was to open up the switches and swap innards. Here is what's in them:
I was expecting springs to jump in my face and get lost but there were no springs.
The four brass crossy things are teeter-totters. The source pin contacts (the center ones) are higher than the two on either side of them, so the brass crosses pivot on them. The plastic sled (center) rocks the brass crosses the opposite way as it moves from one end to the other when the lever (right) is actuated.
It's really super simple. How can something this simple go bad? Well, here's what the base of the OEM switch looked like on disassembly:
You can see that greenish fuzz on the top right side. The problem was pretty obvious:
The plating was peeling off the steel saddle and, presumably, reacting with the brass contacts and forming the green fuzzy residue through some sort of chemical reaction. I cleaned up the base using vast amounts of CRC contact cleaner followed by Deoxit D5, then I started with reassembly. The new switch essentially consists of all the eBay switch's parts, with only the base of the original switch being retained. Here is the finished product:
I used a bit of Caig contact grease on reassembly, and the action feels better than the factory switches'. Parallel-grip pliers are a must to re-form the steel saddle and do this job cleanly.
I was pretty happy with the outcome, until I realized my new switch was quite a bit taller than the old one:
It is actually taller than anything else on the main board, but luckily, according to my measurements there will be one whole millimeter left between the top of the switch lever and the case.
Hopefully this will help someone who's having to deal with those ALCO switches 🙂
Last edited:
This is an honorable attempt that I really hope works for you. I just love when we beat the obsolescence system. Keep us informed.
I wonder if flux got into the switch during the assembly of the amp. It was then left in there to react with the metals and the moisture in the air. Corrosion does bad things.
Tom
Tom
You mentioned parallel gripping pliers. I haven't seen a pair of these in years. No, I am not talking about slip joint and the many other possibilities. Parallel gripping is usually a compound levered device that is perfect for crimping the old 'Scotch Loc' connectors that we used in the phone company, but I always knew that they would have other uses within their range of jaw gap. The E9Y pliers that we used might have been just big enough to grab one of these switches.
Miniature vice may work for small jobs, keep small bits of wood handy for reducing gaps if needed, also to protect against jaw marks.
Drill vise is more parallel than ordinary vise.
A bit less fiddly than pliers.
Drill vise is more parallel than ordinary vise.
A bit less fiddly than pliers.
@Ixnay here they are, the mighty powr-kraft parallel-grip pliers.
They don't look like much, but once you have them in your toolbox they have so many uses you never thought about, I honestly don't know how I could do without them at this point. Highly recommended 🙂
You can adjust the jaw gap up to about 1.25" by sliding the rack and pinion mechanism. Is that the same pliers you're thinking?
They don't look like much, but once you have them in your toolbox they have so many uses you never thought about, I honestly don't know how I could do without them at this point. Highly recommended 🙂
You can adjust the jaw gap up to about 1.25" by sliding the rack and pinion mechanism. Is that the same pliers you're thinking?
Last edited:
Meanwhile, my dead PSU is on its way to Siglent. No swapping for a new one, and I have to pay to ship it in (they pay for return shipping).
The service guy helpfully pointed out I could just buy a new PSU from the Siglent website and return it for refund within the 30-day window. That'd cost me another $40 shipping but I don't know, I might.
The service guy helpfully pointed out I could just buy a new PSU from the Siglent website and return it for refund within the 30-day window. That'd cost me another $40 shipping but I don't know, I might.
Never saw those. What can they do a grip pliers, bahco or cobra water pump pliers can not do? I guess it can do all what the others can but then combined?
Specifically they do not operate on a pivot system, but in this case a rack and pinion. The assures that the jaw is in full contact which is particularly important when bending metal. It is a small difference that is very necessary for particular types of work. Pump pliers and most of the rest are rarely grabbing with the whole jaw, and this affects the bending process. I am sure that there are other applications where this contact is needed.
Reminds me of the true parallel wood clamp made by Bessey.
Reminds me of the true parallel wood clamp made by Bessey.
Interesting, not quite as good as rigol's policy then. Within the 30 day purchase window, they definitely pay shipping both ways and in my case offered a new one in exchange. I was not in a hurry and knew in reality they changed the board, which is like a new unit on the waveform gen I bought.