Eros problems

[Wade Winnett]

I recently finished the Eros phono preamp and listened with utter joy for two days until (noise/crackling) reared its ugly head on the A/Black channel.  All Ohm/voltage checks through  the entire build were consistent and well within spec.  Diodes were always immediately and well lite at all checks. The (IB) on the C4S board now showed 235 VDC.  I followed the trouble shooting section of the build manual.  I inspected but never saw an obvious solder issue.  I have removed all boards at least twice in order to inspect and reflow. Most point to solder points were re soldered. When I was dissembling I was able to recheck good voltage on page 40.  I was starting to run out of patients  but  page 55 voltage check confirmed 235vdc. All tubes are NOT heating(illuminating).  I did one last Ohm/voltage check.  Ohms are still good. Voltage numbers are my first and last check.  IA:216.8-297.5, IB:216.4-297.3,OA:164.3-289.2,OB:161.6-295.2, OC:96.6-185.8, OD:96.7-66.8, OKA:97.5-40.2,OKB 97.9-64.4, OKC: 1.412-1.795, OKD: 1.660-1.511. Diodes on the C4S are working, diodes on the shunt regulator are not illuminating.  Fuse was never blown. This is my third Bottlehead amp kit with my Moreplay and Crack with capacitor upgrades.  I also have an Akitika GT-108 power amp, and Zaph audio ZRT2 speaker kit under my belt with few issues.  I have also made my own power and RCA cables. I know that I have a beautiful and exquisite sounding system with the Eros the final piece.  Any help or advice is more than welcome.

[Paul Birkeland]

I was starting to run out of patients  but  page 55 voltage check confirmed 235vdc. All tubes are NOT heating(illuminating). 

You can't have 235V on the voltage checks on page 55 without the tubes being illuminated, so one of these statements is incorrect.


 

IA:216.8-297.5
IB:216.4-297.3
OA:164.3-289.2
OB:161.6-295.2
OC:96.6-185.8
OD:96.7-66.8
OKA:97.5-40.2
OKB 97.9-64.4
OKC: 1.412-1.795
OKD: 1.660-1.511

I think the first thing I would do is to focus on why the regulator output has popped up.  You can't have 235V on the check on page 55 and not have 235V at IA/IB (whichever one that 235V fed).  If the tubes are not illmuniating, what are the DC voltages at the + and - pads of the 6.3V output on the power supply board? (They should be around 50V and 56V)

[Wade Winnett]

So I found a big problem: The 10uf Tantalum capacitor nearest to the 6.3 vdc on the power supply board out is blown apart.  Like a little bomb went off inside it.  Not sure when that happened.

[Paul Birkeland]

That can happen if they are put in backwards, but this is not what happened to your cap.  If you look above it in your photo, the center leg of the 1085 regulator is not adequately soldered.  One or more of these legs coming loose could put excessive voltage across that cap, which will cause it to explode.

[Wade Winnett]

So what is the SOP for getting parts?

[Paul Birkeland]

You can e-mail [email protected], or you could poke around to see if there's a 10uF 10+V rated tantalum capacitor available close by.

[Wade Winnett]

I have replaced  the blown 10 uF Tantalum capacitor on  power supply board,  I'm back to only having voltage discrepancies.  All LED's light up in a non-suspicious manner.  I did voltage checks and some results changed from shortly after energizing to letting everything warm up. Here are my first and last voltage results: IA:216.8-215.7, IB:235-233.1, OA:165.5-169.3, OB:155.6-164.7, OC:96-93.3,OD:96.3-93.4, OKA:96.9-94.8, OKB:97.1-95, OKC:1.079-1.054, OKD:1.117-1.145. I also reflowed the legs of the 1085 regulator as advised. Thoughts?

[Paul Birkeland]

The issue you're having is not related to the 1085 regulator, but rather the high voltage shunt regulator board doesn't seem to be functioning on one side.

Could you report the Kreg voltages on each half of the rear C4S shunt regulator PC board?

[Wade Winnett]

KREG A:  8.0 VDC,  KREG B: 6.7 VDC

[Paul Birkeland]

There's a little pad with an X on it on either side of that rear C4S regulator board, can you measure the DC voltages on each of those X pads?

[Wade Winnett]

A-2.674 VDC,  B-2.474 VDC

[Paul Birkeland]

I would be somewhat suspicious that there's a solder joint on the bottom of that C4S regulator board that isn't 100%.

You had previously reported that the IA voltage at the front C4S board was 300V, but that half of the regulator now appears to be working. 

These kinds of issues can be flaky solder joints, conductive debris around the sockets, or sometimes two connections on a tube socket that are wrapped around the sides of the pins and sometimes touch, and this can cause intermittent voltage faults.

[Wade Winnett]

Well...bad news.  I removed the C4S board for the third time and inspected both sides with no obvious issues.  I reflowed all points on the affected channel.  Now I have bigger issues again.  All LED's on the C4S board light up but NONE of the LED's on the Shunt regulator light up now.  Here are my currant voltage numbers: IA-292, IB-292, OA-264, OB- 289, OC- 175, OD- 77.8, OKA- 64.2, OKB- 73.9, OKC- 1.328, OKD- 1.732.

[Paul Birkeland]

When you have problems like this where things work sometimes and don't work other times, it's bad solder joints or broken wires.  If the LEDs don't light up on the board above the D socket, then you need to focus your efforts there.