jpmorris
Tape Wolf
Okay, so after a productive session last night, which involved using the A807 to do some backwards piano, the machine up and died. The A807 has a particular operating mode where you can press PLAY with the tape unloaded so as to clean the capstan. However, I have never been sure how to get it INTO that mode after use. Sometimes the act of cleaning the rest of the transport will cause the machine to go back into idle, I suspect it may be related to the tape presence sensor.
The machine goes into idle by default, so a quick and dirty way to get the machine into idle is to power it off and power it on again. I don't like doing this because I've been worried for a while that power cycling it too much may damage the machine, and of course that is exactly what happened.
The machine now displays the ROM version, but this never clears and the top two indicator LEDs flash. There isn't a list of fault codes that I can find, but other people who have reported similar antics (including someone with the exact same ROM version as me) discovered that the 15v fuse had blown. Which it has (might have been nice if they could have said '15u' in the LED display?). One reason for starting this thread is to spread the knowledge.
Now, the old fuse was a 2A slow-blow fuse and the only 2A fuses I have don't say if they're fast or slow because I didn't know how to tell at the time. I'm assuming it's a quick-blow fuse - either way, the replacement blew and given the very violent manner in which the original 2A fuse blew I am thinking that it's not just a one-off.
At least two other people have encountered this issue and found that the rectifier for the 15v line had gone short, so I have some replacements on order, just in case. Over the next day or so I'll pull the rectifier board and poke it around to see if that has happened.
Something that worries me a bit is that I can't find drop-in replacements for the ones used on the deck. The low voltage lines have square, 2A 35v bridge rectifiers with a hole in the middle to which the heat sink attaches. The only ones I can find of similar rating (2A 80v) are round and have no way to attach cooling. I appreciate that semiconductor technology has improved in the intervening 29 years since the machine was built. Should I be worried about the replacement overheating, assuming a replacement is needed?
The other thing is that the servicing manual specifies different ratings, e.g. something like 0.8A 250v, two 2A 35v, one 6A 280v(!). Was this done for cost saving, or is there a reason you'd want a lower rating? For instance, a 0.8A 250v bridge rectifier doesn't seem to be a thing. Would it be harmful to put in a 400v 2A unit?
Assuming I can get the machine back on its feet, there is a mod recommended for the rectifier board of putting capacitors over the back of it for surge suppression. This came standard on the MK2, and now I feel like a moron for not adding them when I recapped the machine last year...
The machine goes into idle by default, so a quick and dirty way to get the machine into idle is to power it off and power it on again. I don't like doing this because I've been worried for a while that power cycling it too much may damage the machine, and of course that is exactly what happened.
The machine now displays the ROM version, but this never clears and the top two indicator LEDs flash. There isn't a list of fault codes that I can find, but other people who have reported similar antics (including someone with the exact same ROM version as me) discovered that the 15v fuse had blown. Which it has (might have been nice if they could have said '15u' in the LED display?). One reason for starting this thread is to spread the knowledge.
Now, the old fuse was a 2A slow-blow fuse and the only 2A fuses I have don't say if they're fast or slow because I didn't know how to tell at the time. I'm assuming it's a quick-blow fuse - either way, the replacement blew and given the very violent manner in which the original 2A fuse blew I am thinking that it's not just a one-off.
At least two other people have encountered this issue and found that the rectifier for the 15v line had gone short, so I have some replacements on order, just in case. Over the next day or so I'll pull the rectifier board and poke it around to see if that has happened.
Something that worries me a bit is that I can't find drop-in replacements for the ones used on the deck. The low voltage lines have square, 2A 35v bridge rectifiers with a hole in the middle to which the heat sink attaches. The only ones I can find of similar rating (2A 80v) are round and have no way to attach cooling. I appreciate that semiconductor technology has improved in the intervening 29 years since the machine was built. Should I be worried about the replacement overheating, assuming a replacement is needed?
The other thing is that the servicing manual specifies different ratings, e.g. something like 0.8A 250v, two 2A 35v, one 6A 280v(!). Was this done for cost saving, or is there a reason you'd want a lower rating? For instance, a 0.8A 250v bridge rectifier doesn't seem to be a thing. Would it be harmful to put in a 400v 2A unit?
Assuming I can get the machine back on its feet, there is a mod recommended for the rectifier board of putting capacitors over the back of it for surge suppression. This came standard on the MK2, and now I feel like a moron for not adding them when I recapped the machine last year...
