Panasonic RX-CT810 boombox slow to power up

[John Robertson]

I have this Panasonic boombox, model RX-CT810. It works well once it powers up,
but it is taking about 5 seconds. Kind of like if it was a old tube radio that
you turn on, wait for a few and allow the tubes to warm up. Afterwards it works
fine. It used to power right up, but I have not used it for about a year now.

Everything else works fine, AM/FM, both cassette decks on it, speakers, all
controls, etc. The unit was probably made early to mid-1990s.

At first, I thought maybe the filter eletrolytics were bad, so I replaced them
(2 100uf caps). No difference. The old caps did seem fine, both ESR and
capacitance-wise out of circuit, but I decided to leave the new ones in.


Disconnected the transformer and hooked it up to the meter, it powers on
instantly.

Any thoughts on where else to look?

 

[Jerry G.]

I am not familiar with the particular circuits in your unit, but this sounds
like something in the protection circuits for the output stage is going off
value from age, or whatever. I would do an ESR test of all the caps in the
pre-driver, and output stage areas to start with. There is also a chance
that a component(s) is failing in the pre-drivers or output stage itself,
and the protection circuits are not allowing the output stage to start
working.

The reason for the long delay is the parts in question must be heating up to
drift back to proper value, and then the unit will work. Therefore the fault
may be attributed to part(s) that are thermo fault related.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"John Robertson" <robertson@voicenet.remove.com> wrote in message
news:grdbrvc3laamrpc2tbnp1n5qab4t4fhhkv@4ax.com...
I have this Panasonic boombox, model RX-CT810. It works well once it powers
up,
but it is taking about 5 seconds. Kind of like if it was a old tube radio
that
you turn on, wait for a few and allow the tubes to warm up. Afterwards it
works
fine. It used to power right up, but I have not used it for about a year
now.

Everything else works fine, AM/FM, both cassette decks on it, speakers, all
controls, etc. The unit was probably made early to mid-1990s.

At first, I thought maybe the filter eletrolytics were bad, so I replaced
them
(2 100uf caps). No difference. The old caps did seem fine, both ESR and
capacitance-wise out of circuit, but I decided to leave the new ones in.


Disconnected the transformer and hooked it up to the meter, it powers on
instantly.

Any thoughts on where else to look?

 

[Sofie]

John Robertson:
Do you get the same results when you power the boombox with it's internal
batteries ?
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
------------------------


snipped:

"John Robertson" <robertson@voicenet.remove.com> wrote in message
I have this Panasonic boombox, model RX-CT810. It works well once it
powers up,
but it is taking about 5 seconds. Kind of like if it was a old tube radio
that

> Any thoughts on where else to look?

 

[John Robertson]

Jerry, you were spot on! Turned out one of the caps in the output had gone bad,
new one fixed the problem. Thanks!

On Sat, 15 Nov 2003 05:56:06 -0500, "Jerry G." <jerryg50@hotmail.com> wrote:

I am not familiar with the particular circuits in your unit, but this sounds
like something in the protection circuits for the output stage is going off
value from age, or whatever. I would do an ESR test of all the caps in the
pre-driver, and output stage areas to start with. There is also a chance
that a component(s) is failing in the pre-drivers or output stage itself,
and the protection circuits are not allowing the output stage to start
working.

The reason for the long delay is the parts in question must be heating up to
drift back to proper value, and then the unit will work. Therefore the fault
may be attributed to part(s) that are thermo fault related.

 

[John Robertson]

Sofie, I didn't think to check it with batteries, but did after your comment.
Jerry was right that it was another bad cap. Thanks so much for your help!


On Sat, 15 Nov 2003 07:22:06 -0800, "Sofie" <sofie@olypen.com> wrote:

John Robertson:
Do you get the same results when you power the boombox with it's internal
batteries ?

 

[James Sweet]

"John Robertson" <robertson@voicenet.remove.com> wrote in message
news:59ufrvkdccmcb6m2ak2at7f6dkgrq9k0bs@4ax.com...

Sofie, I didn't think to check it with batteries, but did after your
comment.
Jerry was right that it was another bad cap. Thanks so much for your help!


On Sat, 15 Nov 2003 07:22:06 -0800, "Sofie" <sofie@olypen.com> wrote:

John Robertson:
Do you get the same results when you power the boombox with it's internal
batteries ?

There's been a *ton* of things failing lately with bad capacitors, for me
they've even surpassed cold solder joints as the most common failure.