Hi, looking for a little help repairing a Schiit Saga 1.0. In the tube section the right channel has a huge hum and is distorted. Left channel is fine. The amp is fine in passive mode for both channels. Observation looks like the SMD resistor (6SN7 pin 8) - R114 may be blown . It cooked off the digits so I can't read its correct replacement value, I can't just assume its the same as R214 which is connected to the tube pin 5. My R114 is reading 0.5Mohm in situ.
I checked out the two 2.2uF WIMA caps and swapped them. That's not the issue. There aren't many other components to check out in the tube section, maybe a couple transistors? I don't have a scope.
Attached is an image pointing out the resistor in question. If someone could read the label I would be grateful.
I checked out the two 2.2uF WIMA caps and swapped them. That's not the issue. There aren't many other components to check out in the tube section, maybe a couple transistors? I don't have a scope.
Attached is an image pointing out the resistor in question. If someone could read the label I would be grateful.
Attachments
If you have a head-fi account, Jason is very active there. I bet he'd give you the value if you pm him.
Alternatively, if you are willing to remove the PCB, you could trace the vias (on the underside.... see yellow arrows) and tell us where they go... you could also take a photo of a good resistor - we'll be able to help you with its value. It would also be good to provide the valve type/detail, and then remove the valve and take a photo of the socket.
.... or you could just try Jason, as suggested above...
.... or you could just try Jason, as suggested above...
Does the Saga 1 have ont of those no visible screws enclosures? I need to figure out how to get my Freya+ apart.
dave
dave
Excellent! 152 is 1.5k - thanks! I was tempted just to drop a 1.5k 1/4watt out of my kit there to see what happens - usually not a good idea... 🙂
Well, unfortunately the outside the pad lifted. No idea where to run a jumper, so its possibly kaput.
Last ask on this one. Can anyone provide any guidance on tracing the pad? The other side appears to be connect to a surface mount cap.
I suppose if you could remove the PCB and post the photos of the underside... we might be able to help..??
What valve is that?
The root cause of that SMD resistor blowing up is probably a faulty valve... in other words, even if you replace the resistor(s)... the underlying problem would still be there for you to find.
What valve is that?
The root cause of that SMD resistor blowing up is probably a faulty valve... in other words, even if you replace the resistor(s)... the underlying problem would still be there for you to find.
Well, its a multi-layer board. The resistor in question is connected to pin 8 on a 6SN7. The bottom side of the board isn't populated and you can't see traces only the other side of thru-hole components. The board also runs in passive mode, so I may just use it that way. It uses a pot to drive a series of switched relays to act as attenuator, so its a decently clean sounding pre-amp with remote control. Can you use a high powered flashlight to see the traces?
That's a grid (grid 2), not the filament. Think about how the valve gets plugged into its socket.
The resistors (1.5k) are most likely connected to those big red sound coupling WIMA caps.
The grid got into contact with the plate (most likely) and burnt the SMD resistor. Replace the valve and use a multimeter to test the above...
The resistors (1.5k) are most likely connected to those big red sound coupling WIMA caps.
The grid got into contact with the plate (most likely) and burnt the SMD resistor. Replace the valve and use a multimeter to test the above...
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Not a good idea. Replace both resistors in both channels for new SMD ones of the exact right size and replace the tube.
Can't. The resistor pad went. I think the board is basically toast.
But I have bigger fish to fry. My Aleph J clone is exhibiting some wicket current drain between the PS and the rectifier. I decided to plug it in to try a last hurrah on a pair of speakers I sold. Noticed non-uniform heat come up and hit my face. Once off I checked the jacket on the rectifier connector and its melting...
Cleaning up this mess to the Aleph J on the bench. This should be fun... ugh...
But I have bigger fish to fry. My Aleph J clone is exhibiting some wicket current drain between the PS and the rectifier. I decided to plug it in to try a last hurrah on a pair of speakers I sold. Noticed non-uniform heat come up and hit my face. Once off I checked the jacket on the rectifier connector and its melting...
Cleaning up this mess to the Aleph J on the bench. This should be fun... ugh...
Toast???
That resistor connects to some other component on that PCB.
How to figure it out? Using an ohm-meter:
a) try to contact the remaining trace (or via) near the damaged pad.
-or-
b) assuming L/R channel symmetry, figure out what the other 150 ohm resistor is connected to and find the same point on the channel with the damaged pad.
That resistor connects to some other component on that PCB.
How to figure it out? Using an ohm-meter:
a) try to contact the remaining trace (or via) near the damaged pad.
-or-
b) assuming L/R channel symmetry, figure out what the other 150 ohm resistor is connected to and find the same point on the channel with the damaged pad.
It is fun when using good tools and tidy working. Lifted PCB pads is a nuisance and indeed difficult to solve. Even with lifted pads one usually can find a point to connect to. Just draw the schematic if you don't have the service manual. There is often light at the end of the tunnel.
Ok, I reassembled it for now. Regarding symmetry - it wasn't obvious. I'll have to get back to this project. I cleared it off the bench.
SMD and tubes?
Weird combination of old and new, and the tubes may not be best quality.
Tough to solve, without a tube tester.
Weird combination of old and new, and the tubes may not be best quality.
Tough to solve, without a tube tester.
Weird?! Why? Isn't it good engineering to use parts optimally regardless of (design) age?
The tube won't be top quality but that is standard today. Things don't need to live long. The brand name seems to indicate it.
The tube won't be top quality but that is standard today. Things don't need to live long. The brand name seems to indicate it.
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