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| [#1842] LEAK TL12.1 restoration According to the tube data sheet for 7581A it is "unilaterally interchangeable" with the 6L6GC. Should be good in Leak 12.1? |
hennietaljaard 新會員105.xxx.xxx.140 |
2025-09-01 12:35 | |
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| [#1843] LEAK TL12.1 restoration Re. 1841 As checked the Duncan tube data sheet, 7581A has exactly the same pin-outs as KT66 (including G3 internally connected to cathode), and 7581A anode Va and Vg2 tolerance a are slightly better than KT66's. It should be a good substitute for KT66. On added benefit is 7581A's heater current is 0.9A vis-a-vis KT66's 1.27A, i.e. it consumes lesser current. Soundwise, you should compare by your ears and let us know your findings. 最後修改時間: 2025-09-01 14:03:27 |
rcwy 正式會員 118.xxx.xxx.29 |
2025-09-01 14:00 |
| [#1844] LEAK TL12.1 restoration Thank you kindly for the reply. This morning I replaced the KT66 with 7581A and my first impressions are favorable. After listening for 2 hours I find the sound is clean, chimey, delicate, focused and well balanced. Bass is slightly less (compared to GEC KT66). I will say the GEC has a slightly warmer & natural tone. The differences are small. They are new production Tung-Sol 7581A. I can live happily with them. Other tubes are: Mullard EF37A Mullard ECC33 (yellow print) Mullard GZ32 最後修改時間: 2025-09-01 17:51:45 |
hennietaljaard 新會員 105.xxx.xxx.140 |
2025-09-01 17:49 |
| [#1845] LEAK TL12.1 restoration Hi Has anyone ever encountered an imbalance in volume between their Leak 12.1 amps? I have a problem with one amp playing softer than the other one. I have swopped the valves between the amps but the problem remains. |
hennietaljaard 新會員 105.xxx.xxx.26 |
2025-11-20 04:26 |
| [#1846] LEAK TL12.1 restoration I could also mention the amps had a full recap but some of the resistors are still orginal. The tubes is fine. But weirdly one amp plays softer than the other. Anyone ever encountered this problem? |
hennietaljaard 新會員 41.xxx.xxx.181 |
2025-11-20 14:37 |
| [#1847] LEAK TL12.1 restoration 四/五十年前的老機器，零件愈原裝，毛病愈多，誤差愈大，聲音愈差。 既已拆下舊電容，為何不順道測量一下電阻呢？  |
羅密歐 正式會員 219.xxx.xxx.65 |
2025-11-20 18:22 |
| [#1848] LEAK TL12.1 restoration Re. #1845 (and #1816 & 1819) Are your pair of TL12.1 (of which one unit has "softer") the same as you shown before (pictured below)? Obviously they are very different internally and need to be restored to be the same. Where are you based? USA/UK/? ?   最後修改時間: 2025-11-20 20:37:06 |
rcwy 正式會員 118.xxx.xxx.29 |
2025-11-20 20:31 |
| [#1849] LEAK TL12.1 restoration I have 2 pairs. I am referring to the bottom picture which shows one of a pair. The top picture is a different pair and not part of this question. Referring to the bottom one it looks different now because it was recently recapped and some resistors were replaced. The recap was not done by me because I do not have the skills. But I have since found a solution to the imbalance problem. A very strange thing. I found if I use EF36 in the pair the balance is restored. But with EF37A there is an imbalance. The technician can’t explain it either. I am in South Africa. 最後修改時間: 2025-11-21 19:43:48 |
hennietaljaard 新會員 160.xxx.xxx.66 |
2025-11-21 19:37 |
| [#1850] LEAK TL12.1 restoration Thanks for sharing. South Africa is a very different world and happy to know you and your world. Are there electronic components shops around your town/city, or you must buy from online shops? If you can source your own supplies, try the restoration by yourself, given one of the purposes of LEAK TL12.1 having easy-to-access "tag-boards" is for EASY repair/restoration! I know some idiots in electronics could do restoration themselves. Just read the users manual of a good multi-tester 萬用錶 for measuring AC/DC voltage, ohmage of resistors/coils, capacitance of caps - Just junior secondary school physics is sufficient (if can remember the lessons). You probably need courage and carefulness in handling high voltage e.g. over 100/200V AC, over 400-500V DC more than electronics knowledge. Skills can be grown with more and more practices in using a soldering gun! Back to your concerns about EF36 vis-a-vis EF37A in your TL12.1s, it should be absolutely clear in mind that two normal working EF36/EF37A tubes should give very similar performance (except that EF36 is more sensitive to RF interferences) to the extent that none should be "softer" (except when one of the tubes is in fact weak and out of its spec). Get two new-old-stock (NOS) EF37A tubes to replace them. 最後修改時間: 2025-11-22 06:14:14 |
rcwy 正式會員 118.xxx.xxx.29 |
2025-11-22 06:00 |
| [#1851] LEAK TL12.1 restoration This easy-to-access "tag-board" (same as LEAK TL12.1's tag-board, just when a replacement is needed. I have some stocks)    最後修改時間: 2025-11-22 12:55:56 |
rcwy 正式會員 118.xxx.xxx.29 |
2025-11-22 12:49 |
| [#1852] LEAK TL12.1 restoration Hi Please confirm the specification of the cathode resistor. Is the following correct?: 600ohm, wire wound, 5 to 10 watts? Is this correct? |
hennietaljaard 新會員 41.xxx.xxx.243 |
2025-12-02 16:02 |
| [#1853] LEAK TL12.1 restoration Yes, according to the official schemetics, it is 600 Ohm 5-7 Watt wire wounded. In reality you can find 620 Ohm which is also good and it can extent the life of KT66s. 最後修改時間: 2025-12-02 17:19:41 |
rcwy 正式會員 118.xxx.xxx.29 |
2025-12-02 17:18 |
