Eros has very weak L channel [resolved]

R

Randy morgan

New member
Hi folks, my first post. I finished building the new Eros kit today. I thought I was careful. The R channel sounds fine, the L is very weak though audible. I visually checked every connection, found a couple of solder whiskers, looked for debris, poor/cold  solder joints, replaced the 6922 tube, cables, & more. Check voltages and resistances? I hate to admit I’m a bozo with a multimeter, can’t get correct or reproducible results. I’m don’t have alligator clips. The initial voltages on boards 1 & 2 were fine.  I’ve read most of the relevant posts ( I think)
Any ideas? Thanks,
 
I would post the following voltages:

+275V pad on PSU board
+6.3V pad on PSU board
-6.3V pad on PSU board

IA, IB, OA, OB, KregA, KregB on the board above the D socket

All labeled pads on the front C4S board

-PB
 
I figured out the multimeter, no longer a bozo there. I went through the entire instruction manual step by step. On p. 54 “connect /solder white wire from d8 to A Kreg” Shoot! I had routed both white wires , D3 (correct) AND D8 to kreg B.  Couldn’t believe it. Connected D8 correctly and….. no difference. Couldn’t believe it.  I replaced the 12au7, nope.
There is one voltage way off: OB on the c4s was 108 while OA was 227. Here they all are:

Shunt: IA 306
          IB 304
          OA 227
            OB 227
          KregA. 6.38
          KregB. 7.25

C4S:    IA. 229
          IB  229
          OA 227
          *OB 108
          OC. 101
          OD. 101
          OkA. 104
              B. 101
              C. 1.82
              D. 1.99

Fingers crossed.
                 
         

 
The voltage check on page 55 of the manual would have halted the build so this issue could be addressed.

The board above the 12AU7 is producing the correct voltages, so we can move on to the other board.

Can you post a few photos of the wiring around the EF86 and 6DJ8 sockets?  It would probably also help to see the board above those sockets too.
 
Screen shot of pix have .png extension which is on the allowable list, size is 4 mb, less than the 25 limit, still won’t post. Please refer to your email pix
Thanks again, RM
 
I found them easily enough, 2 are backwards, Doh!
    I was able to remove them, but re-inserting was a disaster, I broke leads on both of them. How do I order 2 replacement parts?
Thanks! I’m finally optimistic that it will eventually work
RM
 
PN4250A transistor x 2
So funny (now).  I stared and stared at all parts & manual photos, I could not see that those 2 were backwards. Thanks for your patience & time.
 
I received & installed the 2 transistors today, and….now the left channel is totally silent. Ah well, at
least I got to email-meet Mrs Doc B, Eileen who sent the parts. I had high hopes. Not sure what to do
now, kind of losing interest. It’s Not the kit’s fault. As I said previously, I thought I was being careful, methodical & I didn’t feel like I was in a hurry. I do now realize my 66 year old focus and concentration is Nothing like it was when I was younger. I probably should have kept my work time to 90 min, & not 2-3 hours.
 
Did you measure voltages before you tried to listen to your kit?  You really have to do that, as bad voltages mean your kit isn't working and could cause unpredictable consequences if you attempt to use it!
 
No I did not measure voltages first, thinking the reversed transistors MUST be the (only) problem.
Wrong again. At least readers of this thread can see what Not to do.
Voltages have gone from bad to much worse

The 3 power board #s are the same

Shunt board all essentially the same except OB is 243 (was 227). & kregB 8.2 (was 7.25)

C4S: IA 245 (was 229).  The other readings not listed are normal/unchanged.
        OA 173 (was 227)
        OB 230 (was 108)
        OD 60 (was 101)
        OkB 58 (101)
        OkD 2.51 (1.99)

What a mess. I wonder if I fried the replacement transistors, or even the entire board. I had to apply heat for a long time to wiggle
The new leads into old solder-y holes, though I did spend quite a bit of time trying to clean the holes first.
    With so many crazy readings I’m thinking I should start over,  buy a new kit , everything except the base and transformer. Costs a bit more but less frustrating. Unless I screw it up again.
Hey I have a great idea! I’d love to have an Eros ii with 1:15 sut (my Shelter 901 is 0.5 mv) BUT built by
YOU. Now that would be sweet. My work is just not that good. I’ve built simple amp kits, but this Eros was much more difficult
Ok ok please advise,
& thanks again PB for your time & effort.
 
Now you have to go back to the board above the 12AU7 socket and figure out why that has stopped working.  The 220V you should have at IA on the front board is determined by proper operation of the board above the 12AU7, which is now no longer functioning properly.

If you remove both the IA and IB wires on the front PC board and let them poke up into the air, what do you see at OA and OB on the C4S board above the 12AU7 socket?
 
You must log in or register to reply here.

Similar threads

R
Quickie 1.1 Measurements Wrong (updated)
Replies
5
Views
17K
Paul Birkeland
Paul Birkeland
C
Getting buzz/hum and mono on crack [resolved]
Replies
9
Views
11K
Caseystonequest
C
Jameson
Quicksand dead again [resolved]
Replies
1
Views
20K
Jameson
Jameson
D
Telefunken ECC88
Replies
2
Views
4K
Dhouse7516
D
J
Needing help using multimeter [resolved]
Replies
9
Views
3K
Thermioniclife
Thermioniclife
Back
Top