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| [#1] Troubleshooting Revox A77 Am a Learner, and enjoy learning a few things from fixing things... this A77 ---Cheerfully brought with unknown issue Quick background - First power up...things seem work for a few sec , then it smoke..End of tape Blub brew, the Capstan motor no longer running......... all the rest of the fast forward , Rewind...etc are ok Since Capstan not running anymore , so the rest is uncertain first check ; 24V Ac Is present , F102 Fuse at one of the power supply section blew so i get a few fuse ( 630ma Slow Blow), it all blew ... so cannot check things further... so first things first... why F102 keep blewwwwwwwwwwwwwwwww ? Seem something is shorted... questions 1 -- if D101 at fault ...will it cause f102 blew ? or 2-- or somewhere down the 21VDC ...seem it is an connection to EOT ( End of tape Senors circuit ) m, it has a short, so F102 blew ? 3)...not sure... wish someone may enjoy some troubleshooting fun , happy to mess around with me... such troubleshooting may inspire the other A77 user to solve their issue..etc..too thx for reading........ nice to learn some simple things..but it seem complicate for me at this stage.. thxxxxxx  最後修改時間: 2022-03-19 00:32:04 |
hahayanyan 正式會員49.xxx.xxx.157 |
2022-03-19 00:28 | |
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| [#2] Troubleshooting Revox A77 https://www.tapeheads.net/showthread.php?t=77697 https://www.tapeheads.net/showthread.php?t=72845 FYI ..... Once these 2 guy fixed the wrong polarity of C101, F102 stopped blowing up....... Google Search Revox A77 F102 |
Kenny 正式會員 42.xxx.xxx.223 |
2022-03-19 00:43 |
| [#3] Troubleshooting Revox A77 thzx kenny first link... the guy made a mistake of wiring after he done some recap... the second link...seem ...my cause...but the guy mounted a Cap wrongly.. haha thx haha 最後修改時間: 2022-03-19 00:59:12 |
hahayanyan 正式會員 49.xxx.xxx.157 |
2022-03-19 00:56 |
| [#4] Troubleshooting Revox A77 This a77 seem never serviced.. At this moment I assume those wiring and components are all untouched.. Haha.. Google ING.. i do notice..there are quite many people...having new issue after recap ,since they put things back with some mistake.., hence i may be the next..haha why not an off topic but nice photo haha  最後修改時間: 2022-03-19 01:41:00 |
hahayanyan 正式會員 49.xxx.xxx.157 |
2022-03-19 01:16 |
| [#5] Troubleshooting Revox A77 Haha, While the fuse was blown at the first time, some isolations should be done such as the rectifier module, dc outs... etc, before trials afterwards. BTW, I like A77, when it came to hk, was named 利獲時，and the agent was likely called 謀得利, old British style of doing things, like, although the sun is set. |
LaLaLam 會員 112.xxx.xxx.200 |
2022-03-19 07:20 |
| [#6] Troubleshooting Revox A77 Yes..and later. Today. Shall try to find where may be the short.. And then st the transistor That is called stupidity or lack of exp... Haha |
hahayanyan 正式會員 180.xxx.xxx.251 |
2022-03-19 09:26 |
| [#7] Troubleshooting Revox A77 Haha 嗰啲usb光管真係好用 That pcb.. 有粒好隱藏性被擋住嘅螺絲... 嘩好似好大工程先拆到出嚟 Today... Measure some resistance.. Around.. And check thsoe diodes and transistor etc... But seem need to remove that pcb.. Haha  |
hahayanyan 正式會員 45.xxx.xxx.35 |
2022-03-19 14:33 |
| [#8] Troubleshooting Revox A77 最近喺幾部 teac A series and this revox A77 內部結構多了一些相處時間 最後修改時間: 2022-03-19 15:37:28 |
hahayanyan 正式會員 180.xxx.xxx.135 |
2022-03-19 15:26 |
| [#9] Troubleshooting Revox A77 For any one like to know more. About this board for your A77 great this guy...give me an good answer ...., the hidden screw... it is enough space to unscrew..without the need to remove the solenoid hahahahaahah ( at his video about 23:30 time mark ) https://mega.nz/file/XohGAJgb#qXAjm0R8u5aZEYBHTEklWLRJP1uBhqA3KrvPToo7cRI  最後修改時間: 2022-03-19 16:02:09 |
hahayanyan 正式會員 180.xxx.xxx.135 |
2022-03-19 15:48 |
| [#10] Troubleshooting Revox A77 need to replace those 2 ...which blockj back current when Solenoid is activated , one of them goes bad.. from the guy said..if once it is on and fuse blew...first thing to check are those 2 diode - D151 Si-diode PAB212 50V - 200mA - 70° - D152 Si-diode BA127 50V - 100mA - 70° some of the A77 version it is D121 ...but not 151 wish i have the correct diode at home..haha unlikely..i have some but unlikely 最後修改時間: 2022-03-19 17:51:39 |
hahayanyan 正式會員 180.xxx.xxx.135 |
2022-03-19 17:50 |
| [#11] Troubleshooting Revox A77 Suppose I can hook up a oscilloscope, install another fuse... And look for the back emf generated by the solenoid coil ramp up, If a bit of luck.. I may able to catch that trigger for blowing the fuse.. Haha Tricky .. Need to think how to.. If I am going to test.. It One channel to fuse one end.. One channel to the other end.. And earth to earth.. Not to chassis.. Or.. Not sure.. Haha Instead of putting 35Vac to that fuse.. I can have a square wave input.. Etc... Anyhow.. I am. Shopping for part.. 最後修改時間: 2022-03-20 23:36:41 |
hahayanyan 正式會員 49.xxx.xxx.6 |
2022-03-20 23:27 |
| [#12] Troubleshooting Revox A77 Haha, direct measurement of solenoid back emf is sometimes dangerous to the oscilloscope. As the emf level is - L di/dt, if L & rate of current is high, the oscilloscope input circuit may be damaged by the back emf which can be in thousand volt. Perhaps circuit isolation can be done part by part for tracing the root cause is more practical. Good Luck！  最後修改時間: 2022-03-21 08:03:10 |
LaLaLam 會員 42.xxx.xxx.100 |
2022-03-21 07:55 |
| [#13] Troubleshooting Revox A77 Haaha 我係絕對懷疑會整壞部示波器 其實我睇電路圖慢慢都睇到亦都明白 why f103 may have issue.. When both soleniod diode failed. But but excatly understand that f102 ( the one u I have issue. Part of my learning.. ) 你畫的你的圖 is voltage嘅狀態 I guess the current is something like that at the turn on 0.1sec haha 應該就係嗰下必定會跌一跌嘅 一刻令f fuse 102 blew.. One of the brake I. E. Soleniod seem not functioning too from a study last nite 所以琴晚就諗 如果我送過sine wave or square wave instead of 36vdc.. Etc.. 但係我會先change 沒有壞嘅 diode 看情況才看看有沒有需要真係要 study further.. 會再細心諗諗 你嘅一啲建議點樣實行 thx Haha  最後修改時間: 2022-03-21 12:02:32 |
hahayanyan 正式會員 49.xxx.xxx.58 |
2022-03-21 11:47 |
| [#14] Troubleshooting Revox A77 from servicing this A77 having one inspiration..., and why not to make a off box power supply for it.. haha OLD school hifi thinking ...2 box is better than 1... haha |
hahayanyan 正式會員 49.xxx.xxx.58 |
2022-03-21 13:32 |
| [#15] Troubleshooting Revox A77 啱啱經過旺角啱啱 麥氏 閂緊門 咁都畀我買到啱用嘅 diodes haha 心急想試一試 Haha |
hahayanyan 正式會員 45.xxx.xxx.11 |
2022-03-21 18:14 |
| [#16] Troubleshooting Revox A77 Haha 依然未搞掂 haha Add oil |
hahayanyan 正式會員 49.xxx.xxx.164 |
2022-03-22 18:07 |
| [#17] Troubleshooting Revox A77 橋式整流無short? 正常咁燒第一件事睇整流先，之後一級一級咁吸起就跟到。 |
kx14cp1 正式會員 45.xxx.xxx.110 |
2022-03-22 19:28 |
| [#18] Troubleshooting Revox A77 Yes... Has to do it the basic and proper way to troubleshoot it.., wait for deliver for thsoe parts.. Preventive and corrective at the c Same time.. 我應該都做曬喺唔拆散曬佢之下 elimliation.. All those rifa cracked.. And leaky motor cap.. Etc.. 一次過 等材料嚟到希望找出病因.... |
hahayanyan 正式會員 45.xxx.xxx.197 |
2022-03-23 10:09 |
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