Bottlehead Forum
Bottlehead Kits => Eros Phono => Topic started by: haiku626 on July 10, 2012, 03:42:02 AM
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Hello Everyone,
First of all I would like to say that I love the Bottlehead sound. Thus far I have built the wonderful Crack and its Speedball upgrade. Recently I embarked on an Eros but have run into some problems when doing resistance and voltage checks. I will admit that I am one of those builders that basically just knows which end of the soldering iron gets hot... Thank you in advance to all who can help me.
Resistance readings out of sync: first # is actual / second # is standard
Terminals
T11: 47 / 0
T12: 121 / 60
T13: 37 / 0
T14: 132 / 71
T15: 47 / 0
Nine pin sockets
B1: 72 /27
B6: 121 / 60
C7: 121 / 60
Voltage readings out of sync:
C4S board right side (B)
bA: 164 / 0
Kreg: 166 / 1
OB: 221 / 100
breg: 218 / 100
On power up 2 of the leds on this side light up but soon fade out
Thank You
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Haiku,
At least you know which end of the soldering iron to grab and which not to grab. You should be fine.
Can you edit (called modify in the top right of your post) and add the expected values for the points you are out of spec with? That will keep us from jumping back and fourth in the manual.
Looking at the schematic says that bA for either channel should be grounded. With it at 164V that says the wire attached is not grounded. Check the solder joints on each end. Use your meter set to the lowest resistance range and measure from bA to the chassis plate then from the terminal (either T1 or T15) to the chassis plate. Both readings should be almost the same as when you touch the meter leads together, usually about 0.1 or 0.2 ohms.
I can't find Kreg on the schematic I have so I'll go upstairs and do some checking.
Ob should be at 100V. It is high because the tube isn't on. So I'll check on this as well.
Which LEDs come on? Is it the two on the A side or the two on the B side? I bet A side.
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Hi Grainger,
Thank you very much for the correct diagnosis of not having the proper ground. I found that I mistakenly attached the wire from T11 to T27 when it should have been T26. Man, my old eyes are playing tricks on me... Fixing this problem placed my previous mentioned resistance issues more or less in sync with the expected values.
Of course I was now really excited and anxious to spin some vinyl, but did a voltage check just to be sure.
This time all readings on the B CS4 board were okay except for OA which gave a reading of 99 vs an expected value of 170 and Kreg which gave a reading of .59 vs 1.00. I noticed all LEDs light up on this CS4 but the two on the B side were delayed in doing so when compared to the other boards.
Anyway I tried to listen to some music with the Eros regardless of the out of sync reading of OA and Kreg. To my disappointment, no sound out of the left channel. Oh well I should have expected it. Hopefully you or someone else with expertise can help me.
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Haiku, I'm 62, my eyes play the same tricks on me. I spent yesterday, on and off, getting LEDs (diodes) in 4 C4S boards in the right direction.
Some LEDs come on after others. It has to do with where in the circuit they are and how quickly the heater on the tube warms up. As long as they are all on, that is good.
So... opening the Eros schematic... assuming that it is the Kreg on the left channel, there is a lot in that circuit.
You will need to look closely at this board. Check these components for orientation and that it is the right value. The transistor leads can be a pain.
2200uF@4V, small silver cap
2N222 transistor, again small, silver, near that cap
27k ohm 1W resistor
174 ohm resistor
The two above resistors turn on the transistor. If they are swapped it won't come on and the EF86 won't turn on.
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Hi Grainger,
All of the resistor values check out to expected value, the 2N222 transistor and 2700uf capacitor are oriented properly. I am thinking that the EF86 tube does go on since there is some warmth to it when touched after it is left on for a few minutes.
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Check the tube pin voltages. The low voltage at kreg suggests the servo is trying to lower the EF86 plate voltage (should be 100v at pin 6) so either there's a wiring error or possibly the EF86 is not conducting well. The voltage check is the best way to determine where the problem is, but you can swap EF86s to see if the problem moves, and if the tube is warm you can let it run for a while to see if the emission kicks in.
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D'oh! (https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi244.photobucket.com%2Falbums%2Fgg7%2FGrainger49%2FSmiles%2FSlapHead.gif&hash=e5c580c3cfdf525c26703ae0328aefb586b04de5)
Swapping tubes is always the first and easiest idea. See if the problem follows the EF86 when you swap them.
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Swapped the tubes between A and B; however, the problem remained at B. Shucks, I was really hoping that it would be a tube problem...
Kreg: .05VDC / s/b 1
OA: 101VDC / s/b 170
Pin B6 voltage checked out at 102.6
I rewetted some of the soldering where I thought it may help but no luck in improving the readings.
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It's pretty easy to create solder bridges between the small pads on these boards, done it myself a couple of times. It wouldn't hurt to re-inspect the boards for these.
Cheers,
Shawn
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There may be a solder bridge between the two -reg connections closest to the long edge of the board with the LG 2700 and black wire. Does this matter?
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If they are both -reg, they are all supposed to be connected by the trace on the PCB. But the problem comes when adjacent outputs get bridged.
Did you check the component values listed above? Those are in the Kreg circuit. Then verify that R1 on the A side of this board is indeed 113 ohms. That sets the current for the C4S feeding OA.
And don't feel alone, I'm having fits with 11 year old boards I decided to install on Tuesday. It is posted in the Legacy folder.
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Hi Grainger,
Thanks for comforting me. Without the support from the Forum members I think I would be getting a nervous breakdown. Everyone's help has been much appreciated.
I will check the R1 value when I get home from work. I live in a different time zone so you'll see my reply Fri morning.
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I verified my visual inspection of the closely soldered connections for unwanted bridges with my meter especially with the transistors and did not find a problem.
All of the component values for R1 A and B, R2 A and B, R3, and R4 were found to be within their expected values. Pin B6 voltage also checked out okay at 101.4
I rechecked the orientation of the capacitors and transistors along with the correct positioning of the leads.
Kreg still at .059 s/b 1.0
OA at 100.6 s/b 170
Should I try running the amp for a few hours to see if something kicks in or will I be wasting my effort? I have never had it powered up for more than 15 minutes since the tube swapping did not move the problem to the other side.
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Since OA is not up to voltage the cathode voltage, Kreg, would follow. I should have spotted this earlier, sorry.
I'm printing out the schematics now.
I think the two LEDs that glow and turn off are in that OA circuit. The transistors are not turning on properly so they are not passing the voltage to OA. Look at the picture on the bottom of page 29 of the manual. Verify the resistance of R1, 113 ohms, the resistance of R2A, 120K, and that you didn't swap the two transistors (not likely because of the shapes) in this circuit. There are only 6 circuit elements and the LEDs glow so the other four are left.
I will add to this post knowing you are going to troubleshoot later.
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The center tube (socket C) voltages would help. Inspect the wiring while there, especially whether C6 and C7 may be shorted to each other. B6 goes to C7 (assuming I have identified the parts correctly) and OA to C6, and unless there is a short I can't see how they might have the same voltage.
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Grainger said to go and study the diagrams so instead of reading the instructions over and over, I looked at the picture of the finished Eros on pg 79.... Okay, I have to admit that I did something really stupid. I got R2A and R2B inverted which then caused me to also invert R1A and R1B because I used the color of the R2 resistor as a guide. I removed all of them and placed them in their proper location.
Voltage Readings for the side B PC board are now KReg: .92 s/b 1.00 and OA is at 160 s/b 170vdc. These two past problems are now history, and the good news is that the left channel now has sound.
The bad news is, and I hate to drive everyone nuts, but now the other (A side) PC board has weird voltages and no sound. I might have jostled something on the A PC board when removing and reinstalling the resistors on the other B PC board.
Kreg: 5.01 s/b 1.0vdc and Breg: 139 s/b 100vdc. I tried swapping the tubes and still don't have any sound and the voltage readings stay the same.
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Sounds like the same thing. But were these voltages good to start with?
If the voltages were good, then it is a loose solder joint. Start by rewetting the solder pads where the wires are and where the wires land. You will have to take out the screws to get to everything.
A "rewet" is taking your solder iron, put a little solder on the tip and put it on the joint. When the joint becomes liquid count 1-2-3 (about two seconds) and remove the solder pen.
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I rewetted all solder joints on the A side PC board except for the LEDs since they all light up. Also rewetted all terminals and tube pins where the wires from the board connect. Still no sound on the right channel.
Kreg still out of acceptable range at 4.91vdc s/b 1.00
OB: 139 s/b 100
Breg: 139 s/b 100
OA: 140 s/b 160
Here are the tube pin voltages. Possibly Grainger, Paul, Noskipallwd, or others can diagnose the readings to guide me.
Socket C:
1: 143
2: 139
3: 139
4: -
5: -
6: 162
7: 94
8: 95
9: -
Socket A:
1: 139
2: -
3: 5
4: 6
5: -
6: 139
7: -
8: 5
9: -
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OK, the servo (kreg) is not regulating the EF86 voltage. The relevant kreg connects to A3.
That involves the 2N2222, the 174 ohm resistor R3, and the EF86 cathode A3. I assume the EF86 in socket A is lit up, since it has the right filament voltages at pins 4 and 5. It will be difficult to test the voltages on the 2N2222, but that might narrow the field. At least check voltages on the 174 ohm resistor R3, and the correct terminals on the 2N2222.
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Hi Paul,
The 2N222 transistor is oriented properly with the tab toward the middle of the board. The lead closest to the tab is in the middle hole.
I am not getting a voltage reading from R3 the 175 ohm resistor, and no longer can get its rated resistance reading from it (reads only .2)
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Haiku
. . . were these voltages good to start with?
If the voltages were good, then it is a loose solder joint. . . .
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Hi Grainger,
Yes, the readings for kreg were good before at 1.21vdc and the R3 resistor did test good at 174. But now the readings for kreg are 4.91 s/b 1 and R3 is .2 s/b 175.
If I am taking the R3 resistor reading directly from its 2 wire leads on both side of the resistor, would the reading matter if I had a bad solder somewhere? I thought that I was isolating the meter reading to the resistor only by doing this.
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The 2N2222 may be damaged; its base and emitter are across the 174 ohm resistor. (The earlier grounding problem may have exposed the transistor to too much voltage.)
Of course it's possible that those two leads are just shorted on the board, either by a solder bridge or a stray wire. Bright light and a magnifying glass are in order - and plenty of patience, it's a pain to unscrew the board and get it to where you can see the underside. If you can't locate a short then you'll have to remove the transistor to test it and re-test the resistor. I expect when the transistor is out, the resistor will measure normally, in which case just replace the transistor with a new one. Contact Eileen on Monday to get a replacement.
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Hi Paul,
There was no short on the board for the R3 resistor so I removed 2N2222. R3 is still giving a .2 reading. Can you tell me how to test 2N2222. All the advice that I have been getting is much appreciated.
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That's unexpected! Remove R3 and re-check its resistance - if it is 174 then there's a short on the board, if it's still 0.2 then the resistor is shorted - extremely unusual! - but it would explain the data.
For the transistor, check resistance from base (pin 2) to emitter (pin 1), and base to collector (pin 3). You may have to google "2n2222 datasheet" to identify the pins. Do each check in both directions. They should read very high in one direction, low in the other - a few hundred ohms, not zero - actual value depends on your meter.
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Paul,
R3 removed from the board reads 173.4
2N222
Base to 1: 0
Base to 3: 0
1 to Base: 463.5
3 to base: 459.6
I suppose I have a short on the board; I don't see any readily visible bridges except where they share the same trace.
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Zero seems improbably low, but both junctions seem to rectify - so I'm not quite sure what to think. These readings will be different on different meters, which is a pain.
Check the 174 on the other (working) board (without unsoldering) - if it is also zero, then the zero does not indicate a problem. If it's 174 or close, then replace the 2N2222.
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Hi Paul,
Sorry but the 2N2222 reading should be OL (over limit) not zero for Base to 1 and Base to 3. Does this change your recommendation to replace the 2N2222?
R3 reading on the good side (left channel) is okay at 173.5.
R3 on the bad side reads 173.4 taken off the board and .2 again when put back in the board even with the 2N2222 removed. If I place the resistor in R3 on the A side of the board it reads 173.4.
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Yes it does change - the 2N2222 is OK by this test, as is the resistor. There is a short somewhere on the board, or a mis-connection. One end of R3 goes to -reg which is grounded; the other end to the transistor (terminal "r"), to R4, and to terminal "x" - if any of these are grounded, that would be the problem.
If you can't find it, at some point you'd do better to just build and install a new board. Eileen can help with that if necessary.
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Hi Paul,
I have examined the board using a magnifying glass and have reviewed the manual instructions for the board along with comparing the wiring to the good board. I don't see any possible bridges except where traces are shared at breg and kreg. Can something at socket D or the shunt regulator PC board affect the readings that I am getting, or is this eliminated from causing the problem that I am experiencing? I want to make certain that I cover all areas before calling Eileen for a rebuild of the C4S board.
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You can trace wires from the other terminals I mentioned, or disconnect those terminals from the rest of the preamp. IF the board is not connected to anything else, and is correctly wired without shorts, then there can't be a short at R3 ...
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Paul,
I removed the wires that are connected to the board one by one and took a reading after each wire was removed. R3 reads about .2 at each step and when the C4S board was totally free of the amp, the resistor at R3 still reads .2
Flipping the board over and examining it closely with a magnifying glass, I still could not find any bridges that would cause a short; I even had my wife, who is younger and has better vision, look it over. Other than this I wouldn't know what to look for in what is causing the short. I am pretty much "stumped."
Removed from the board the resistor reads properly at 173.5.
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First, let me say I'm sorry this has become such a frustrating problem! Happens to all of us, and we never get used to it ... but we will resolve it, one way or another!
The likeliest place for a short is between the "A" and "r" pads where the 2N2222 installs. Less likely is near the jumper which goes from bA to bB; the adjacent terminals marked "x" should not be connected to anything. Be sure to look on both sides of the board. Those are the only ones I can see.
If that doesn't help, I think you should contact Eileen, mention this thread, and ask for a replacement board and parts. Sometimes it's less work to do it again than the figure out what went wrong.
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I would like to say that I am taking this as an invaluable learning experience. I am very grateful for the support of all who have contributed, and this has been the driving force for me. Along with that I have also had a sample of the Bottlehead sound that I will be rewarded with although the experience has come from just one channel. A Conrad Johnson PV11 has been my phono source for the past 20 years; nice tubey sound but noisy.
Will examine the board closely in the areas that you mentioned this evening when I get home from work.
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Don't feel rained on, as we used to say. I have been building kits since 1965 and Paul Joppa had to tell me I swapped the input and output wires in my installation of C4S boards last week.
We all get to a point that we can't see what we don't see. Chill out, have a cold, adult beverage and get someone else to look at it as you read out what should be connected where.
You are at the point that you can't see the forest for the trees.
And give a cold, adult beverage to the guy who finds the mis-wired element after he finds it.
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I hope none of you thought I had given up since I have not posted in a week. I did have two other people look over my build of the boards which were found to be built as per instructed, and no obvious solder bridges were noted. Why R3 is shorted is still a mystery. Therefore, I took Paul's advice to order new parts, and rebuild the board. I also ordered a replacement on/off switch that was received defective, and a Bottlehead Badge which I forgot to order initially.
There was small box in my mailbox when I came home Monday evening from the Queen. I initially told myself that I would save the build for the weekend, but could not resist starting the board rebuild at 9:00 PM. I had it finished and installed by 10:30 and did the voltage check. Kreg was still a little high at 1.34VDC but a far cry from the former 4.91; all other readings were okay within the acceptable margins. I wanted to but didn't dare hook up the Eros to my system to see if I had sound in both channels. A failure would have devastated me and I would not have been able to go to sleep.
When I got home from work on Tuesday evening, I swapped out the defective on/off switch and hooked the Eros up to my Conrad Johnson preamp, and gave the Bottlehead Crack with Speedball upgrade the honor of the initial sound check instead of using my power amps and speaker set up. I put the Neville Brothers "Yellow Moon" disc on my turntable and crossed my fingers as the stylus hit the vinyl.
Man, I never new what I have been missing for the past 40 years of listening to records! The Eros soundstage was unbelievable, and its gain is very generous with my Soundsmith cartridge. The bass was solid and deep, and the highs caught me off guard. I guess I had become accustomed to the laid back sound of my CJ and the Eros had much more low end slam and sparkle on the upper end. I am very impressed with the Eros and it's not even broken in; sort of reminds me of the Crack sounding very good without any break in time. I would like to congratulate Paul Joppa, Doc, and the Queen on an exceptional audio component.
I would also like to extend a special thank you to Paul Joppa, Grainger, and Noskipallwd for their assistance when I had difficulties in the Eros construction. The problem that I had with the board added a special challenge that provided a learning experience for me. Again, thank you for the much appreciated support.
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Congrats on your success! I agree with your assessment of the sound quality, it does sound great right out of the box. It will get better though. Before I built the Eros I found myself listening to my digital rig more often, mainly for ease of use. Listening to vinyl most of the time now, thanks to the Eros.
Cheers,
Shawn
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I'm with Shawn, after my Eros build I have hardly turned on the CD player.
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This is a great read for someone expecting his new Eros.