Crown D-150A Filter Caps & Current Draw

[misterc57]

This model is the D-150A with aluminum faceplate, two volume pots and a power switch knob on the front panel.

I took this in trade and it has been sitting for years waiting for me to check it out. Found no power. Bad power switch jumped.

Unit turns ON now but there is a hum present with no input connections and both volume pots at zero. After a few seconds of being ON the amp is drawing 3 amps which seems excessive. Anyone know what this amp should be drawing for current?

There are two large main filter caps, 9400 uF 50V. Schematic shows rails at + and - 45V..

I disconnected the caps, one read 9336 uF, the other 11.56 mF. Not sure the difference in display mF vs uF. I removed both and the 11.56 mF has a bulge leak.

Anyone have experience replacing or sourcing these (9400 uF Aluminum Electrolytic Capacitors - Screw Terminal) capacitors? Substitutes available or not recommended?

Thank you, MC

[x-pro]

11.56µF must be replaced
In general, shake those capacitors in your fist.
If something rattles inside, replace it.

[Helmholtz]

1mF means 1000µF, so 11mF is 11000µF.
Schematic shows 9400µF = 9.4mF.

While the cap with the broken vent should be replaced, I don't think the cap is causing the high current.
Do you have DCV at the output?
If yes do not connect a load.

Please post complete schematic.

[x-pro]

Yes. I misprinted. 11560uF

[g1]

service manual attached

[Helmholtz]

Anyone know what this amp should be drawing for current?

Spec says 30W consumption at idle.
Corresponds to 250mA mains current at 120V.

[misterc57]

I do not have a PDF editor to break out the schematic from the service manual G1 attached.

Tomorrow I will reconnect the caps and check for DC on the output with no load.

Thank you

[Jon Snell]

I do not have a PDF editor to break out the schematic from the service manual G1 attached.

Tomorrow I will reconnect the caps and check for DC on the output with no load.

Thank you

Here you are, both versions attached;

[misterc57]

With no load attached I see a lot of VDC on the output. As I dial up the variac the VDC rises on both channel outputs.

At 75 VAC on the variac I am seeing 25 VDC on both output channels.

Oddly I am not seeing a big rise in current anymore.

This should be fun!

[Helmholtz]

Oddly I am not seeing a big rise in current anymore.

No wonder as the current was caused by the load, heating it by 80W. Very bad for a speaker voice coil.

Star with verifying power rail voltages.

[misterc57]

Rails read good, + and - 45 VDC

[misterc57]

VDC at 3990 B, - 44.8
VDC at 3990 C, - 44.8
VDC at 3990 E, 43.8

VDC at 3990 B, 43.9
VDC at 3990 C, 43.8
VDC at 3990 E, 44.6


VDC at 3991 B, - 44.8
VDC at 3991 C, - 44.8
VDC at 3991 E, 43.7

VDC at 3991 B, 43.9
VDC at 3991 C, 43.8
VDC at 3991 E, 44.6

[g1]

Which is your version? Does it have R237 at Q214 emitter?

[Jon Snell]

VDC at 3990 B, - 44.8
VDC at 3990 C, - 44.8
VDC at 3990 E, 43.8

VDC at 3990 B, 43.9
VDC at 3990 C, 43.8
VDC at 3990 E, 44.6


VDC at 3991 B, - 44.8
VDC at 3991 C, - 44.8
VDC at 3991 E, 43.7

VDC at 3991 B, 43.9
VDC at 3991 C, 43.8
VDC at 3991 E, 44.6

Just a thought, you are reading with 0v as your reference ... you probably are as I have just notived the + and - readings.

IC1 check supply rails are there; R3 and R8.
The correct way to write a capacitors value now woulld be;
9100uF = 9k1uF. 11000uF = 11k0 uF.
11mF has not been used in the industry for many decades.

[misterc57]

Which is your version? Does it have R237 at Q214 emitter?

Yes it has R237 and R137