I have a device (a Roland TR-505 drum machine) that works only on batteries. When I insert the AC adapter (the original, which obviously worked at one time) the device shuts down. The AC adapter appears to be converting the correct voltage at the plug. I don't know much about testing circuit boards. Any ideas as to why this pattern is occurring? Any leads on what I might do to figure out how to repair device without spending a lot of money. It's an old device but it does it's job well and suits my needs when it is working correctly.

Do you have a Volt meter to test that there is at least the proper
voltage coming out from the adaptor? It would be best to test it while
it is connected to the drum machine, so that it is properly loaded. A
no load test may not indicate its true performance.

If the adaptor is working, then check for any opened connections such as
bad contacts, connector(s), and etc in the electrical path from the
adaptor in to the drum machine.

The next step would be to troubleshoot the electronics of the devices in
question, which is something that cannot be done over an email. At this
point, you will have to give it out, unless you are trained, tooled up,
and experienced at this sort of work.

--

Jerry G.
======

"Kevin Ross" wrote in message
...
I have a device (a Roland TR-505 drum machine) that works only on
batteries. When I insert the AC adapter (the original, which obviously
worked at one time) the device shuts down. The AC adapter appears to be
converting the correct voltage at the plug. I don't know much about
testing circuit boards. Any ideas as to why this pattern is occurring?
Any leads on what I might do to figure out how to repair device without
spending a lot of money. It's an old device but it does it's job well
and suits my needs when it is working correctly.

Kevin Ross wrote:

I have a device (a Roland TR-505 drum machine) that works only on
batteries. When I insert the AC adapter (the original, which obviously
worked at one time) the device shuts down. The AC adapter appears to be
converting the correct voltage at the plug. I don't know much about
testing circuit boards. Any ideas as to why this pattern is occurring?
Any leads on what I might do to figure out how to repair device without
spending a lot of money. It's an old device but it does it's job well
and suits my needs when it is working correctly.

If the unit works on batteries but not on the adapter, then it is
probably safe to assume that the power the unit needs is not being
provided by the adapter. This could be due to a faulty adapter or a
regulator circuit in the unit that is not converting the input from the
adapter properly. There might be a bad rectifier, bad capacitor, open
conductor, or any number of faults even if the adapter is good. Only by
opening up the unit and taking measurements can you arrive at the reason
it will not work with the adapter.

Ken wrote:
If the unit works on batteries but not on the adapter, then it is
probably safe to assume that the power the unit needs is not being
provided by the adapter. This could be due to a faulty adapter or a
regulator circuit in the unit that is not converting the input from the
adapter properly. There might be a bad rectifier, bad capacitor, open
conductor, or any number of faults even if the adapter is good. Only by
opening up the unit and taking measurements can you arrive at the reason
it will not work with the adapter.

There is one thing to check first. Most of the time, there is a small
switch to switch of battery power when you connect an adapter. This
switch is often integrated in the connector, and could be open.

---
Met vriendelijke groet,

Maarten Bakker.

"Kevin Ross" bravely wrote to "All" (12 Dec 04 12:42:17)
--- on the heady topic of "AC Adapter Question"

KR From: "Kevin Ross"

KR This is a multi-part message in MIME format.

Use only ASCII text, not MIME encoded, on usergroups, please!


KR I have a device (a Roland TR-505 drum machine) that works only on
KR batteries. When I insert the AC adapter (the original, which obviously
KR worked at one time) the device shuts down. The AC adapter appears to
KR be converting the correct voltage at the plug. I don't know much about
KR testing circuit boards. Any ideas as to why this pattern is occurring?
KR Any leads on what I might do to figure out how to repair device
KR without spending a lot of money. It's an old device but it does it's
KR job well and suits my needs when it is working correctly.

I have had a TR-505. You can test your adaptor with a 100 ohm resistor
and a DC voltmeter. If it reads very low then the adaptor is bad.
There may be a broken rectifier or the filter cap is dry. However,
what you may have is a problem with the adaptor plug battery switch.
It may be simply dirty, so try inserting and removing the plug a few
times. It may also be damaged or have a broken solder pad. This could
be fairly hard to fix if you are not experienced in mechanical things.
To get at the jack the main circuit board has to be removed but it is
a tricky job that requires some experience to know what you're doing
or you might damage the pots or the LCD display. If you don't know how
to solder then do not pass GO, and don't even reach for a screwdriver.
This is vintage 8 bit stuff... ;-)

A*s*i*m*o*v

.... If plugging it in doesn't help, turn it on.

Ken wrote:
If the unit works on batteries but not on the adapter, then it is
probably safe to assume that the power the unit needs is not being
provided by the adapter. This could be due to a faulty adapter or a
regulator circuit in the unit that is not converting the input from the
adapter properly. There might be a bad rectifier, bad capacitor, open
conductor, or any number of faults even if the adapter is good. Only by
opening up the unit and taking measurements can you arrive at the reason
it will not work with the adapter.

There is one thing to check first. Most of the time, there is a small
switch to switch off battery power when you connect an adapter. This
switch is often integrated in the connector, and could be open.

---
Met vriendelijke groet,

Maarten Bakker.