rowe amp problem

On Nov 30, 2:38*am, dan14 wrote:
On Nov 25, 7:17*am, kreed wrote:



On Nov 24, 9:08*pm, Alan Hood
wrote:

Hi,
If the amplifier is the 125 watt type then check that the two DSC1 pre
amp lamp are still connected at each side of the volume control socket,
if one of these is open circuit or the wire is broken off then that
channel will not work.
Some people replace these with a resistor but prefer the lamps.
Yes the ic's can go on the pre amp but not that often.

Regards
Alan

Alan Hood
ami-man
UK
kreed;689619 Wrote:

On Nov 23, 11:02*pm, dan14 wrote:-
On Nov 22, 4:18*am, kreed wrote:

-
On Nov 22, 7:16*pm, kreed wrote:-
--
On Nov 22, 2:17*pm, Tim wrote:--
--
On Nov 21, 5:34*pm, kreed wrote:--
--
On Nov 22, 7:54*am, dan14 wrote:--
--
My rowe r92 will only produce sound out of the right channel. I
swapped the wires for the phono speakers from right to left and
the
problem stays the same. Swapped driver boards in the amp, no
change.
All fuses and transistors test good on amp. Measured for
continuity
from cartridge to amp and that's fine. Also swapped in a known
good
transformer assembly and same. Speakers are all good. I don't have
a
spare amp to see if that's where the problem is but I think it
must
be. I also replaced most caps in the amp and resoldered any
suspect
connections. Not sure where else to look. Any help would be
great.
Thanks, Dan--
--
Pre amp. *The ICs fail--
--
Check you connections at the needle,and as indicated above.May be a
pre-amp problem or a connector issue.--
--
Thats also a good point. *IF its an R-83 or later, simply reversing
the cartridge plug - at either end, or turning the "stereo/mono"
switch to "mono" . * If this makes a difference it will show that it
is the cartridge or associated wiring that is the problem--
-
Also check wiring to the volume control. *Make sure that the 5 way
plug is inserted with the holes facing upwards, and check the wiring
on the back of the terminal strip on the amp cover, as well as
checking that the jumper is in the right position.-
-
The 13 way connector in the middle of the chassis must be the right
way round also. I have found in the past that if this is backwards,
this will result in loss of audio in one channel.-

Thanks for the responses. I've checked all the connections and
reversed connections to see if the problem changed channels but
nothing new just no sound from left channel. Do the IC's fail very
often in the preamp and are they still available? Thanks-

It is an extremely common fault in my experience. They either fail (no
sound) or distortion occurs, of it the one in the volume control
circuit fails, volume changes at random.

They are a strange type that are available, but I cant remember the
details. *If you get the type number from the IC and do a search on
this group history, it was discussed extensively a couple of years back

--
Alan Hood

Yes, I clean forgot that one.

We used to replace them with dial lamps as used in car stereo, (will
withstand vibration) and use silicon sealant to "glue" them to the
board and also provide some shock/vibration resistance.

The idea of these bulbs is that when there is normal operation and
minimal current is flowing through the volume control, they will
appear as close to zero ohms (cold resistance), but if the volume
control leads were accidentally shorted to mains power, or some other
high voltage that could damage the amplifier, the zener diodes (15v
from memory) on the other side of the bulb would conduct, thus
connecting the bulb directly across this high voltage. *The bulb would
blow pretty soon, and as such protect the circuit from damage

I only saw this happen once, where the cable for the control was
somehow stapled through the phone line that went to a public phone in
the hallway (that of course rarely ever rang). connecting one leg of
the volume control to connect to one wire in the phone cable. *It
caused very nasty intermittent bulb blowing, and loss of one channel
(dual volume control was being used) and the only thing that stopped
me bypassing the bulb was seeing how it was blown so violently. *The
100v pulses that come down the line to ring the phone bell were
probably what was taking it out.

Being a coin operated line, it might have been some other signal in
the cable that came, as there would have to be some form of pulses or
signalling from the exchange to cause coins to drop as spent (held in
escrow in the phone, and returned if not used) when making long
distance calls that varied in number of minutes per coin depending on
distance, time of day and so on.

A voltage to ground with everything disconnected was discovered, and
manual checking of the cable run revealed the problem.

The bar owner when told of this was extremely concerned that private
conversations might have been amplified into the public areas (maybe
he was ringing hookers, or SP bookmakers or something) , but informed
him that in this system it was technically impossible to happen.

Thanks for all the input. Still no sound from left channel. It's a 130
watt rowe amp so I don't see the two lamps like in the 125 watt amp. I
tried another amp and both channels worked so now I at least know the
problem is with the amp. As I said earlier, I swapped the driver
boards and installed new transisitors. Checked and resoldered any
suspect joints and replaced most of the caps. I just pulled all 6 of
the ic's, socketed them and swithed the ic's from right channel to
left to see if the problem switched sides and it didn't. Not sure what
else to try.


Mute relay ? once had the contacts on one one side got welded closed
by a lightning strike (that didnt involve the actual machine)

Originally Posted by dan14[_2_]

On Nov 25, 7:17*am, kreed wrote:[color=blue][i]
On Nov 24, 9:08*pm, Alan Hood
wrote:









Hi,
If the amplifier is the 125 watt type then check that the two DSC1 pre
amp lamp are still connected at each side of the volume control socket,
if one of these is open circuit or the wire is broken off then that
channel will not work.
Some people replace these with a resistor but prefer the lamps.
Yes the ic's can go on the pre amp but not that often.

Regards
Alan

Alan Hood
ami-man
UK
kreed;689619 Wrote:

On Nov 23, 11:02*pm, dan14 wrote:-
On Nov 22, 4:18*am, kreed wrote:
[color=green][i][color=darkred][i]
-
On Nov 22, 7:16*pm, kreed wrote:-
--
On Nov 22, 2:17*pm, Tim wrote:--
--
On Nov 21, 5:34*pm, kreed wrote:--
--
On Nov 22, 7:54*am, dan14 wrote:--
--
My rowe r92 will only produce sound out of the right channel. I
swapped the wires for the phono speakers from right to left and
the
problem stays the same. Swapped driver boards in the amp, no
change.
All fuses and transistors test good on amp. Measured for
continuity
from cartridge to amp and that's fine. Also swapped in a known
good
transformer assembly and same. Speakers are all good. I don't have
a
spare amp to see if that's where the problem is but I think it
must
be. I also replaced most caps in the amp and resoldered any
suspect
connections. Not sure where else to look. Any help would be
great.
Thanks, Dan--

Hi Dan,

On the jumper plug (13 pin) is there a link between pin 2 & pin 7? There should be on the 130 watt amp.
If the link is fitted I honestly think it is time to send in the amplifier for repair, if you are in the USA then Bruce Wentworth is your best bet or myself in the UK

Regards
Alan

Alan Hood
ami-man
UK