Bottlehead Forum
Bottlehead Kits => Eros Phono => Topic started by: ideal.hat on October 22, 2024, 06:45:03 AM
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I’ve had my Eros since 2017, and there’s always been a bit of background hum that worsens as I increase the volume. I’m listening through Crack and Mainline amps into multiple 250-300 ohm headphones.
I’ve neglected addressing the hum for a few years, so I’m a bit rusty. However, today I performed a resistance and voltage check, hoping to sort this out with some help. I can’t send the unit in for repair since I live in Denmark, and the cost of shipping would be significant.
Here’s what I’ve done so far:
Measured the resistance on the small brown resistors on the B board—all three show correct values, so I don’t think they’re mixed up.
Reflowed some suspicious solder joints, particularly at B3, B6, T10, and T15.
Tried a different 6922 tube, but there wasn’t much of a change.
Swapped the EF86 tubes, but that didn’t make a significant difference in the values either.
Below are my resistance measurements:
Terminal strips:
| Terminal | Value |
| 1 | 0 |
| 2 | 85,3k |
| 3 | 0 |
| 4 | 74,8 |
| 5 | 0 |
| 6 | 465k |
| 7 | 465k |
| 8 | 0 |
| 9 | 46,4k |
| 10 | 46.5k |
| 11 | 0 |
| 12 | 74,8k |
| 13 | 0 |
| 14 | 85,3k |
| 15 | 0 |
| 16 | |
| 17 | |
| 18 | 0 |
| 19 | 46,8k |
| 20 | 0 |
| 21 | 0 |
| 22 | 0 |
| 23 | 0 |
| 24 | 0 |
| 25 | 0 |
| 26 | 0 |
| 27 | 46,9 |
| 28 | 0 |
| 29 | No connection |
| 30 | No connection |
| Input/Output | Channel | Specified Resistance | Measured Resistance |
| Input Jack | Left (black) | 47K ohms | 46,9k |
| Input Jack | Right (red) | 47K ohms | 46,8k |
| Output Jack | Left (black) | 470K ohms | 465k |
| Output Jack | Right (red) | 470K ohms | 465k |
Nine pin sockets :
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
| A | 27k | 0 | * | * | 0 | 74.8k | 0 | * | 47.1k |
| B | 26.9k | 0 | * | * | 0.5 | 74.8k | 0 | * | 47.1k |
| C | 46.5 | 75k | * | infinity | 0 | 46.6 | 75k | * | 0 |
The voltage check seems a bit off:
| Socket Side | Kreg (VDC) | OB (VDC) | bA (VDC) | breg (VDC) | OA (VDC) | IA (VDC) |
| Socket A | 1.377 | 98.3 | 0 | 99.6 | 163.9 | 223 |
| Socket B | 0.616 | 66 | 0 | 70.7 | 206 | 224 |
I am having problems with posting pictures, I get the following Error 500.
I have uploaded some photos to imgur.
https://imgur.com/a/TGettrT (https://imgur.com/a/TGettrT)
Please let me know if I should run additional tests or provide photos to help diagnose the issue. Any guidance would be greatly appreciated.
Thanks in advance for your help.
@forum moderators: I get the following error when I post .jpg pictures, you might be able to see more about it in your logs.
This page isn’t working right now
forum.bottlehead.com can't currently handle this request.
HTTP ERROR 500
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The good news is that your shunt regulator looks to be working properly, but the bad news is that one C4S board up front has voltages that are way, way off.
The easiest first step to take is to swap those two boards up front between sides to see if that 0.6V moves to the other side of the amp or stays put.