Hello, everyone. My first post in the forums 
I just messed up my 300B sockets soldering and I was wondering if …
Thanks a lot. Best regards.
I just messed up my 300B sockets soldering and I was wondering if …
- Anyone has upgraded the stock 4 pin sockets? It seems there’s not much space between the board and the top plate so not sure if replacing those sockets is an easy task.
- Anyone knows if the Elekit 4 pin tube sockets can be purchased as spare parts. I asked Elekit and an European distributor about that but I had no response yet :/
Thanks a lot. Best regards.
Hello, @vkung .
I don’t want to replace them but I made some mistakes soldering them. Big solder drops melted inside the pin holes and I’ve been unable to perfectly desolder/clean them. Now the tubes do not fit in the socket holes :/ Rookie mistake.
I didn’t know they were made in Korea. I think I found manufacturer’s website:
http://belton.eparthosting.co.kr/yc/shop/item.php?it_id=4-6
Thanks a lot!
I don’t want to replace them but I made some mistakes soldering them. Big solder drops melted inside the pin holes and I’ve been unable to perfectly desolder/clean them. Now the tubes do not fit in the socket holes :/ Rookie mistake.
I didn’t know they were made in Korea. I think I found manufacturer’s website:
http://belton.eparthosting.co.kr/yc/shop/item.php?it_id=4-6
Thanks a lot!
Hello, @vkung
I have found a German distributor that sells both models:
https://www.tubeampdoctor.com/belton-vtb9-pt-novalfassung-platinenmontage-mit-goldbeschichtung
https://www.tubeampdoctor.com/belton-vtb4-st-4-pin-fassung-loetoesen-mit-goldbeschichtung
Thank you so much!
I have found a German distributor that sells both models:
https://www.tubeampdoctor.com/belton-vtb9-pt-novalfassung-platinenmontage-mit-goldbeschichtung
https://www.tubeampdoctor.com/belton-vtb4-st-4-pin-fassung-loetoesen-mit-goldbeschichtung
Thank you so much!
Hello, @findog3103.
I don’t think that is the correct volumen attenuator unit in a TU-8900 amplifier.
Mine is labelled as UNIT-3 instead of your UNIT-2. Also, the unit is not a square form like yours. It’s wider on the back of the unit exactly to avoid the issue you are facing.
See attached images of my UNIT-3 (volume attenuator) and UNIT-2 (RCA inputs).
Green UNIT-3 is the stock one. Red UNIT-3 is a mod I purchased in HiFiCollective.
Stock UNIT-2.
Hope it helps.
I don’t think that is the correct volumen attenuator unit in a TU-8900 amplifier.
Mine is labelled as UNIT-3 instead of your UNIT-2. Also, the unit is not a square form like yours. It’s wider on the back of the unit exactly to avoid the issue you are facing.
See attached images of my UNIT-3 (volume attenuator) and UNIT-2 (RCA inputs).
Green UNIT-3 is the stock one. Red UNIT-3 is a mod I purchased in HiFiCollective.
Stock UNIT-2.
Hope it helps.
Hello, everyone.
I’m facing some problems during my TU-8900 sound tests and maybe someone can point me to the right direction in order to find the root cause of my problem. I’ll try to explain the steps I made in order to debug the issue.
TL;DR:
Right channel sounds terrible due to a high amount of distortion and voltage checks on every right channel point are significantly lower than expected.
Steps I followed so far:
1. Switched left and right channel power tubes (300B) with no improvement in sound nor measures.
2. Switched left and right channel voltage tubes (12AU7) with no improvement in sound nor measures.
3. Switch both power and voltage tubes with no improvement in sound nor measures.
4. Switched left and right output transformers (Lundahl LL2787C) with no improvement in sound nor measures.
5. All electrolytic capacitors are correctly oriented. (Double checked that).
6. Diodes, bridge diodes and zener diodes are correctly oriented.
7. I started measuring all voltage check points as the manual suggest. Every right channel value is significantly lower than expected:
Can anyone suggest more tests? Any method I could use to test input voltages? Or capacitors?
I really appreciate any suggestions. This is my first DIY kit
Best regards and thanks a lot for your help.
I’m facing some problems during my TU-8900 sound tests and maybe someone can point me to the right direction in order to find the root cause of my problem. I’ll try to explain the steps I made in order to debug the issue.
TL;DR:
Right channel sounds terrible due to a high amount of distortion and voltage checks on every right channel point are significantly lower than expected.
Steps I followed so far:
1. Switched left and right channel power tubes (300B) with no improvement in sound nor measures.
2. Switched left and right channel voltage tubes (12AU7) with no improvement in sound nor measures.
3. Switch both power and voltage tubes with no improvement in sound nor measures.
4. Switched left and right output transformers (Lundahl LL2787C) with no improvement in sound nor measures.
5. All electrolytic capacitors are correctly oriented. (Double checked that).
6. Diodes, bridge diodes and zener diodes are correctly oriented.
7. I started measuring all voltage check points as the manual suggest. Every right channel value is significantly lower than expected:
| Check point | Standard voltage | Read voltage left channel | Read voltage right channel |
| 1 - 2 | 2.8V | 2.67V | 0.6V |
| 3 -4 | 70V | 74.9V | 23.54V |
| 5 - 6 | 75V | 77.8V | 23.54V |
| 7 - 8 | 205V | 199V | 47.2V |
| 9 - 10 | 0V | 3mV aprox | 10 mV aprox |
| 11 - 12 | 60V | 60.4V | 13.3V |
| 13 - 14 | 65V | 65.4V | 18.43V |
| 15 - 16 | 390V | 380V | 104V |
| 17 - 18 | 405V | 393V | 106V |
| 19 - 20 | 330V | 314V | 82V |
| 21 - 22 | 420V | 416V | 127V |
| 23 | 6.2V | 6.4V |
Can anyone suggest more tests? Any method I could use to test input voltages? Or capacitors?
I really appreciate any suggestions. This is my first DIY kit
Best regards and thanks a lot for your help.
Fixed it. It just needed to be put on first before putting the volume plate on.
I am currently building the 8600S and am really enjoying the process. This is my first kit amplifier. I bought all top of the line upgrades. I am taking my time and triple checking every step I am taking ! The directions are excellent and everything was packed nicely ! Victor has responded quickly to any questions I have had ! I am taking my time with this build and could not be happier ! I am glad to be part of this forum and appreciate everyone's comments ! Thank you...