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Old 2nd September 2019, 03:27 AM   #11
HeavyNova is offline HeavyNova
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Check what you installed for R55 and R56.

If you go by the Japanese schematic you get R55=3.3M and R56=470k.

If you go by the English instructions, you get R55=470k and R56=10k. ��

I'm in the process of the build myself and still unsure which R55, R56 values are actually correct (although my guess is that the original Japanese schematic is more likely correct)

I zoomed in on completed build photos of the TU-8500 online and found that unfortunately half the people are building them with incorrect resistance for R55 and R56 and are not aware.

Last edited by HeavyNova; 2nd September 2019 at 03:46 AM.
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Old 2nd September 2019, 04:05 AM   #12
HeavyNova is offline HeavyNova
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Here are completed, online photos of TU-8500 builds with the resistor 'variation' you have to look out for.
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File Type: jpg Screenshot_20190901-215315.jpg (125.1 KB, 110 views)
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Old 2nd September 2019, 04:29 AM   #13
WKCox is offline WKCox  United States
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Elekit TU-8500 Preamp Kit Build - My First Build
R55 and R56 just set the mute relay delay, so not critical as long as the delay is long enough to mute power on transients.
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Old 2nd September 2019, 12:26 PM   #14
HeavyNova is offline HeavyNova
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OK, so what are the correct values for R55 and R56? Does anyone know?
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Old 17th September 2019, 04:52 PM   #15
HeavyNova is offline HeavyNova
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Hello, I just finished the build and am getting no output and don't know why or what else to check to isolate the problem.

I have checked voltages at both test points. I got 136.2V at the 140V test point and 12V/12.12V at the two 12V test point(s). Tubes light up. LED stays off when turned on unless I push down hard on either the CN1 or CN7 connector, although both connectors are snapped perfectly in place and solder joints all look good underneath. Even when I get the LED to temporarily light up, there is still no output.



I was extremely careful, neat and tidy with my assembly and took my time while waiting for parts to arrive and complete the build. All resistors installed with mirrored, symmetrical color bands on both sides and larger caps lined up to the best of their ability. At initial startup, there was no pops or smoke or anything- just complete silence. All components still look good and correct, polarity has been properly observed (from what I can tell) but there is still no sound.


Pictured are ShuGuang Sounds of Nature 12AT7's. I also tried the Chinese 12AU7's to rule out the tubes- there is no sound output with either set of tubes. * I circled wrong test point on the photo for the 12V tests. Does anything look out of place or does anyone have any idea what may be wrong? Thank you.
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File Type: jpg Elekit TU-8500F.jpg (738.0 KB, 75 views)

Last edited by HeavyNova; 17th September 2019 at 05:19 PM.
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Old 17th September 2019, 05:55 PM   #16
HeavyNova is offline HeavyNova
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Update* I got a 12.12V reading at the remaining, single 12V test point (so that TP appears good as well) and interestingly, I can also get the LED to light up if I push down on any of the 3 square diodes at the bottom..
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Old 17th September 2019, 07:58 PM   #17
HeavyNova is offline HeavyNova
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Starting new thread.
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Old 18th September 2019, 12:15 AM   #18
mikejr83 is offline mikejr83  United States
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HeavyNova, I don't mind if you want to troubleshoot on this thread.


It looks like you've done some alterations in your build. What have you changed?


FYI, if you're not getting the LED to light up I'd check warm-up circuit.

Last edited by mikejr83; 18th September 2019 at 12:18 AM.
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Old 19th September 2019, 12:59 AM   #19
HeavyNova is offline HeavyNova
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Hey! I got it all worked out and it sounds terrific. Mea culpa. It was a loose shared ground binding post screw connection and two unsoldered relay joints I missed.

I changed a few selected pairs of resistors to precision wirewound vishay/dale, a few electrolytics to higher voltage elna silmic ii that tested out better than the originals for uf, ESR. I kept microfarad values stock. Gold plated heavier duty ceramic tube sockets, gold plated mill-max opamp sockets, vintage NOS Philips polycarbonates, polystyrenes and even a pair of ERO MKT1822 poly's in the phono section to replace a few of the red metalized capacitors and finally a new matched pair of ShuGuang 12AT7 'Sounds of Nature' tubes to replace the stock Chinese 12AU7's.

Last edited by HeavyNova; 19th September 2019 at 01:22 AM.
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Old 19th September 2019, 02:15 PM   #20
mikejr83 is offline mikejr83  United States
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Yea!!! Glad you got it sorted!
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