AMI B

Bought my first ami b model juke. extremely nice cosmetically. when i
turn it on the turn table just spins. . changer is at rest. the turn
table plugs into the junction box. ones ive worked on before plugged
into the amp. does the amp have anything to do with the turntable. i
did replace the fuse and heard the relay in the box on the mechanism
chatter briefly. all halp appreciated thanks norm.

On 4/10/2011 9:16 AM, em pinball wrote:
Bought my first ami b model juke. extremely nice cosmetically. when i
turn it on the turn table just spins. . changer is at rest. the turn
table plugs into the junction box. ones ive worked on before plugged
into the amp. does the amp have anything to do with the turntable. i
did replace the fuse and heard the relay in the box on the mechanism
chatter briefly. all halp appreciated thanks norm.


Yes the amp has to power up and energize a relay for the TT motor.

On Apr 10, 11:16*pm, em pinball wrote:
Bought my first ami b model juke. extremely nice cosmetically. when i
turn it on the turn table *just spins. . changer is at rest. the turn
table plugs into the junction box. ones ive worked on before plugged
into the amp. does the amp have anything to do with the turntable. i
did replace the fuse and heard the relay in the box on the mechanism
chatter briefly. all halp appreciated thanks norm.


If it has a selenium rectifier in the 28vdc, this may be giving low
output due to age. This
may result in the voltage collapsing under load, then coming up
again,
repeating over and over and leading to the chatter as the voltage
rises and falls.

The relay is likely to be powered from a 28vdc supply

Measure the DC voltage at the power supply box, especially when the
relay chatters.


(Note that I have never seen a model B, am giving general advice based
on the G here.)

On Apr 13, 1:26*pm, kreed wrote:
On Apr 10, 11:16*pm, em pinball wrote:

Bought my first ami b model juke. extremely nice cosmetically. when i
turn it on the turn table *just spins. . changer is at rest. the turn
table plugs into the junction box. ones ive worked on before plugged
into the amp. does the amp have anything to do with the turntable. i
did replace the fuse and heard the relay in the box on the mechanism
chatter briefly. all halp appreciated thanks norm.

If it has a selenium rectifier in the 28vdc, this may be giving low
output due to age. *This
may result in the voltage collapsing under load, then coming up
again,
repeating over and over and leading to the chatter as the voltage
rises and falls.

The relay is likely to be powered from a 28vdc supply

Measure the DC voltage at the power supply box, especially when the
relay chatters.

(Note that I have never seen a model B, am giving general advice based
on the G here.)



Scrub that,

After seeing Tony's post, I found the schematic, http://www.verntisdale.com/schem/ami-b.jpg

The relay is indeed in the amp, and relay coil seems to be driven by
(in series with) the valve output stage, seems to turn on the relay
when there is sufficient
current passing through the output stage. Seems a very odd way to
design it.


As a starting point, I would plug the TT directly into the mains, so
you can play a record and see if the amp has sound for starters.

The capacitor across the relay is another trouble spot worth looking
at. If this is leaky, it could result in the relay coil dropping in
and out
depending on the audio.

If the sound is no good, this is probably the cause of the relay not
closing and holding correctly.

On Apr 12, 11:08*pm, kreed wrote:
On Apr 13, 1:26*pm, kreed wrote:



On Apr 10, 11:16*pm, em pinball wrote:

Bought my first ami b model juke. extremely nice cosmetically. when i
turn it on the turn table *just spins. . changer is at rest. the turn
table plugs into the junction box. ones ive worked on before plugged
into the amp. does the amp have anything to do with the turntable. i
did replace the fuse and heard the relay in the box on the mechanism
chatter briefly. all halp appreciated thanks norm.

If it has a selenium rectifier in the 28vdc, this may be giving low
output due to age. *This
may result in the voltage collapsing under load, then coming up
again,
repeating over and over and leading to the chatter as the voltage
rises and falls.

The relay is likely to be powered from a 28vdc supply

Measure the DC voltage at the power supply box, especially when the
relay chatters.

(Note that I have never seen a model B, am giving general advice based
on the G here.)

Scrub that,

After seeing Tony's post, I found the schematic,http://www.verntisdale.com/schem/ami-b.jpg

The relay is indeed in the amp, and relay coil seems to be driven by
(in series with) the valve output stage, seems to turn on the relay
That goofy relay/cathode setup was designed to keep the machine from
playing before the output tubes had warmed up. There was no stay-warm.
The obvious problem is that as the tubes age cathode current
decreases, it is probably low now and causing that "chatter" also if
the filter across it dries up (very likely now) audio will appear
across that relay.

Frankly, AMI and later Rowe never did a good stay warm in their tube
amps. After the above setup, they went to a scheme that opened the B+
from the 5U4 not just in standby, but -between records-! This really
pummeled both caps and transformer. Their later stereo amps atleast
used a bleeder resistor to keep a slight charge on the filters but
really..who designed this stuff.

I modded the gray amps in my H-I-J by adding a relay connected to the
scan control which in-turn controlled the input power (AC) to the amp
and changed the mute connections so that it didn't open the B+. I did
notice that on the units with AVC box AMI actually used the unmuting
inrush to hasten the AVC un-squelch (compression release) so I had to
modify that circuit too.

I considered the late-50s AMIs to be the best constructed and have
the best potential for true sound quality, but there were some really
odd engineering choices made.

Rob




when there is sufficient
current passing through the output stage. *Seems a very odd way to
design it.

As a starting point, I would plug the TT directly into the mains, so
you can play a record and see if the amp has sound for starters.

The capacitor across the relay is another trouble spot worth looking
at. *If this is leaky, it could result in the relay coil dropping in
and out
depending on the audio.

If the sound is no good, this is probably the cause of the relay not
closing and holding correctly.

On Apr 14, 7:05*pm, Rob in NYC wrote:
On Apr 12, 11:08*pm, kreed wrote:

On Apr 13, 1:26*pm, kreed wrote:

On Apr 10, 11:16*pm, em pinball wrote:

Bought my first ami b model juke. extremely nice cosmetically. when i
turn it on the turn table *just spins. . changer is at rest. the turn
table plugs into the junction box. ones ive worked on before plugged
into the amp. does the amp have anything to do with the turntable. i
did replace the fuse and heard the relay in the box on the mechanism
chatter briefly. all halp appreciated thanks norm.

If it has a selenium rectifier in the 28vdc, this may be giving low
output due to age. *This
may result in the voltage collapsing under load, then coming up
again,
repeating over and over and leading to the chatter as the voltage
rises and falls.

The relay is likely to be powered from a 28vdc supply

Measure the DC voltage at the power supply box, especially when the
relay chatters.

(Note that I have never seen a model B, am giving general advice based
on the G here.)

Scrub that,

After seeing Tony's post, I found the schematic,http://www.verntisdale.com/schem/ami-b.jpg

The relay is indeed in the amp, and relay coil seems to be driven by
(in series with) the valve output stage, seems to turn on the relay

That goofy relay/cathode setup was designed to keep the machine from
playing before the output tubes had warmed up. There was no stay-warm.
The obvious problem is that as the tubes age cathode current
decreases, it is probably low now and causing that "chatter" also if
the filter across it dries up (very likely now) audio will appear
across that relay.


Is the whole amp turned off when the mech is at rest then ?

Frankly, AMI and later Rowe never did a good stay warm in their tube
amps. *After the above setup, they went to a scheme that opened the B+
from the 5U4 not just in standby, but -between records-! This really
pummeled both caps and transformer. *Their later stereo amps atleast
used a bleeder resistor to keep a slight charge on the filters but
really..who designed this stuff.


Oh dear, I see the problem now. I guess they learnt with experience
over time
I was quite happy with the sound of these too, and the JEL amps, when
they were set up
properly.

The G-80 I had sounded brilliant with records from that era, but with
modern
(80-90's) records, it showed its limitations. IIRC that the top end
was cut off, as records back
then didn't have the high frequency range of those later on.


I modded the gray amps in my H-I-J by adding a relay connected to the
scan control which in-turn controlled the input power (AC) to the amp
and changed the mute connections so that it didn't open the B+. *I did
notice that on the units with AVC box AMI actually used the unmuting
inrush to hasten the AVC un-squelch (compression release) so I had to
modify that circuit too.

*I considered the late-50s AMIs to be the best constructed and have
the best potential for true sound quality, but there were some really
odd engineering choices made.

Rob

when there is sufficient
current passing through the output stage. *Seems a very odd way to
design it.

As a starting point, I would plug the TT directly into the mains, so
you can play a record and see if the amp has sound for starters.

The capacitor across the relay is another trouble spot worth looking
at. *If this is leaky, it could result in the relay coil dropping in
and out
depending on the audio.

If the sound is no good, this is probably the cause of the relay not
closing and holding correctly.

On 4/14/2011 5:05 AM, Rob in NYC wrote:

Frankly, AMI and later Rowe never did a good stay warm in their tube
amps. After the above setup, they went to a scheme that opened the B+
from the 5U4 not just in standby, but -between records-! This really
pummeled both caps and transformer. Their later stereo amps atleast
used a bleeder resistor to keep a slight charge on the filters but
really..who designed this stuff.

AMI was always "different". Even in the later solid state amps they
went the opposite way and leave the amp powered up as long as the juke
is plugged in, even if it's turned off! Never quite understood that one.
Tony

On Apr 15, 1:24*am, Tony Miklos wrote:
On 4/14/2011 5:05 AM, Rob in NYC wrote:



Frankly, AMI and later Rowe never did a good stay warm in their tube
amps. *After the above setup, they went to a scheme that opened the B+
from the 5U4 not just in standby, but -between records-! This really
pummeled both caps and transformer. *Their later stereo amps atleast
used a bleeder resistor to keep a slight charge on the filters but
really..who designed this stuff.

AMI was always "different". *Even in the later solid state amps they
went the opposite way and leave the amp powered up as long as the juke
is plugged in, even if it's turned off! *Never quite understood that one.
Tony


And to make it even more confusing, this is done in only the 120v
models. 240v ones - all turns off, including the amp. (this is also
documented in the shop service manual)

I think in the manual it was to allow paging, and a "remote power on"
device behind the bar. Still doesn't explain why the 240v models
missed out on this.

I only ever had one location where they wanted a power switch behind
the bar, and in this case we just ran mains cable from out of the juke
to a standard household 10a light switch behind the bar next to the
volume controls.

On Apr 14, 10:24*am, Tony Miklos wrote:
On 4/14/2011 5:05 AM, Rob in NYC wrote:
The biggest probelm I had with Rowe SS amp was MM1 (I still have two
MM1 hideaways in service in retro diners) . Again, they had the amp
mains switched -between records- and to make matters worse, the muting
relay actually shorts the output of the amp rather than just the pre-
in. This combination is deadly to output transistors as the
switching transient thump hits a dead short! The biasing diode setup
was primitive but workable. I added a relay to the scan control that
turned them amp and TT motor on at the beginning of a session (that
also eliminated a micro sw) and reworked the whole mute and AVC system
as well as improving high response in the preamp and driver
sections. There is still very slight crossover distortion but the
amps is not used at low enough levels for this to matter.

The physical build quality of the Rowe amp/machines was very good but
again, didn't anyone review these designs?





Frankly, AMI and later Rowe never did a good stay warm in their tube
amps. *After the above setup, they went to a scheme that opened the B+
from the 5U4 not just in standby, but -between records-! This really
pummeled both caps and transformer. *Their later stereo amps atleast
used a bleeder resistor to keep a slight charge on the filters but
really..who designed this stuff.

AMI was always "different". *Even in the later solid state amps they
went the opposite way and leave the amp powered up as long as the juke
is plugged in, even if it's turned off! *Never quite understood that one.
Tony