Bottlehead Forum
Bottlehead Kits => Eros Phono => Topic started by: David E on July 02, 2024, 09:23:16 AM
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OK, I'm a newbie. Finished the build, all volts were spot on along with resistance checks. BUT it sounds awful. I installed the 4 transistors backward on the c4s board and had to remove and reinstall them, was hard to do, so I'm wondering if I got them too hot and burned them. Would that make it sound bad?
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Can you post all the voltages on your small front PC board?
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1A = 218.5
1B = 219.5
OA = 156.3
OB = 160.7
OC = 97.8
OD = 97.2
OKA = 98.1
OKB = 98.0
OKC = 1.54
OKD = 1.72
All 8 - Led's light up.
All readings are VDC
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Can you post some build photos? While your voltages aren't completely out of whack, they also aren't exactly correct, but the operation of both EF86s and the 6922 is a bit suspect, like maybe some resistors on the front PC board got swapped around by accident possibly or something of that nature. I would not expect this to sound good at all with that set of voltages.
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Paul, Thanks for all the help but I can't seam to get a picture for you, need to fine one of my grandchildren to help me. I get one in the attachments and then it says when I post file to big. How to make the picture smaller???
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Not very sharp, I'll try again hope this is better.
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Who said, you can't teach old dog new tricks. Hope this makes things more clear. Thanks for all your help. DLE
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I would reheat the MJE350 transistors on the front C4S board, with a special focus toward the middle leg of each one.
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Thanks for the reply, I reheated all 4 transitstors on the C4S board, I think I burned them up when I turned them around the first time. there are my volt reading now:
1A - 218.5
1B - 218.9
OA - 157
OB - 161.7
OC - 97.3
OD - 96.6
OKA - 97.5
OKB - 97.4
OKC - 1.483
OKD - 1.536
All readings are VDC
I hooked it back up and know change in sound.
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It wouldn't hurt to try a different 6922.
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What your though on the four transistors on the C4S board. Before I spend money on a vault.
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They appear to be doing what they are supposed to be.
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First I would like to thank Bottlehead for sending me a 6922 tube at no charge, but it didn't fix the problem. Paul where should I look next? Should I take the voltage again?
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Yes, recheck the voltages with the 6922 you've received.
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OK, Here we go again, voltages with new 6922 Tube:
1A - 218.5
1B - 219.1
OA - 155.6
OB - 160.8
OC - 98.0
OD - 97.7
OKA - 98.6
OKB - 98.5
OKC - 1.49
OKD - 1.55
All 8 - LED's Light up
All reading are VDC
Looks like biggest diff. is between OA and OB, but what would that mean?
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Do you have one channel that's now sounding correct?
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Paul, That was good thinking, but No both channel failed. I've started doing a complete rebuild
on paper with a check list. I'm on page 52 now.
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Well I went over everything again and I only found that in a couple of places I used the Lower instead of Upper solder point. would that make a difference. Check out my notes on page 47, item 5, last on the page. My reading on resister was high 48, 60 ohms. Where do I go from here. DLE
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I would reflow the rest of the non-LED solder joints on that center front C4S board.
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OK, PB but this is a stupid question, is it best to remove the C4S board and reflow from the back or careful reflow from the front?
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Definitely reflow from the back.
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Still sounds like shI*, here are the voltages as of reflowing the C4S board:
1A - 218.5 VDC
1B - 219.1
OA - 155.8
OB - 160.2
OC - 98.0
OD - 98.0
OKA - 98.7
OKB - 98.7
OKC - 1.53
OKD - 1.50
PB, I'm flustered but thanks for sticking with me through this, DLE
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Given your voltages, I wonder if the issue is the bias of the 6922 tube. I had a problem with my Eros2 sounding bad for no reason I could account for, and Paul Joppa eventually diagnosed the problem as the bias of the 6922 tube. The Eros needs at least a 1.5v difference between OC/D and OKA/B. Less than that and you get distorted sound.
I was unable to fix mine. It's in the cue to go to PB for repair.
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Scroll down a few posts to see PJ's take on my unhappy Eros.
https://forum.bottlehead.com/index.php?topic=15304.30 (https://forum.bottlehead.com/index.php?topic=15304.30)
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When I take these on for repair, typically it's a matter of reflowing solder joints, and an occasional mistake. It's tough to offer a whole lot more than that. Occasionally I see a dead 6922 that will cause similar issues to what you have, but swapping that tube hasn't yielded much in the way of results.
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PB, in your opinion is the problem most likely in the C4S board? I played my turntable directly in to my S.E.X last night and it was great, is the problem in the output of my table? Does my turntable already have a pre-amp in it, its a Audio-Technica AT-LP120XUSB?
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Yes, that TT has a phono preamp built in. There is a "phono/line" switch on the back. Set it to "Phono" to bypass the built-in preamp and use the Eros instead. (Set it to "Line" to direct connect the TT to the S.E.X. amp. See the downloadable manual on page 8.)
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Well Damn, I been chasing stupid. All's well in the South, Thanks a million and the Eros sounds amassing.
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LOL :^)
On the plus side, you did eventually identify the real problem!
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Yes, that TT has a phono preamp built in. There is a "phono/line" switch on the back. Set it to "Phono" to bypass the built-in preamp and use the Eros instead. (Set it to "Line" to direct connect the TT to the S.E.X. amp. See the downloadable manual on page 8.)
That seems a little backward. Shouldn't the switch in the "phono" position mean the preamp (with RIAA correction) is engaged. And when in the "line" position, just the unaltered signal (no RIAA) which would then require an external phono preamp?
These labels can indeed be confusing sometimes. If indeed that is the way, I too would have done it the same way as David. But, yeah the manual is usually (but not always) the correct way.