Show Posts
16
Reel to Reel Tape Machines / Re: PLL Capstan Light on A810
« on: March 02, 2014, 05:06:11 PM »
Sorry for being late to the post.
There are simple problem areas to look for quick fix fist:
One is to look at the capacitive techo sensor output from the capstan motor. Its functions are described in the section 3.5.9 in the manual.
Second is as Doc B had suggested - there are three electrolytic caps (c12 100uF 16VDC, C16 10uF 16VDC, C18 2.2uF 16V) in the capstan control board need to be replaced. Even the youngest A810s with serial numbers >6000 are still more than 30 years old.
However, most likely reason for losing PLL signal that I had been experiencing was due to failure of L1 and L2 variable inductors in the capstan control board from machines with serial numbers older (smaller) than ~4000s region.
One of the things that are less than Studer-like was to use these cheap variable inductors with very questionable quality. These old inductors used some plastic like material to hold the ferrite core in place after being tuned to 5.5Mhz +/- 500Khz. I found most of the ferrite cores to be out of place due to the holding material that had gone soft from age and no longer holds.
Since I hadn't been able to locate these variable inductors, the only solution was to temporarily position the ferrite core to its proper position and fix it with epoxy glue. As it dries, I have to double check with a digital scope with counter capability to make sure it holds 5.5Mhz signal.
Hope it helps.
Ki
There are simple problem areas to look for quick fix fist:
One is to look at the capacitive techo sensor output from the capstan motor. Its functions are described in the section 3.5.9 in the manual.
Second is as Doc B had suggested - there are three electrolytic caps (c12 100uF 16VDC, C16 10uF 16VDC, C18 2.2uF 16V) in the capstan control board need to be replaced. Even the youngest A810s with serial numbers >6000 are still more than 30 years old.
However, most likely reason for losing PLL signal that I had been experiencing was due to failure of L1 and L2 variable inductors in the capstan control board from machines with serial numbers older (smaller) than ~4000s region.
One of the things that are less than Studer-like was to use these cheap variable inductors with very questionable quality. These old inductors used some plastic like material to hold the ferrite core in place after being tuned to 5.5Mhz +/- 500Khz. I found most of the ferrite cores to be out of place due to the holding material that had gone soft from age and no longer holds.
Since I hadn't been able to locate these variable inductors, the only solution was to temporarily position the ferrite core to its proper position and fix it with epoxy glue. As it dries, I have to double check with a digital scope with counter capability to make sure it holds 5.5Mhz signal.
Hope it helps.
Ki