Howard 418

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Howard 418

Post by Motorola man on Tue Mar 12, 2013 7:47 pm

I've completely recapped and replaced all of the resistors and it sounds great. Well, almost. There is absolutely no bass (the low frequencies, not the fish. Although there's no fish in it either). I've cleaned and tested the pots, and have even substituted fixed resistors with no luck. I've also swapped the 6F5G tube as well as the bias cell (the thingy between the two 1 meg resistors). At this point, I'm stumped. Any advice?
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Re: Howard 418

Post by Motorola man on Tue Mar 12, 2013 7:48 pm


Here's the schematic for the bass circuit.
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Re: Howard 418

Post by Dr. Radio on Tue Mar 12, 2013 8:50 pm

How are the ground connections from the bass control pot, bass network capacitors etc?

If the radio relies upon rivets for connections to the chassis, sometimes these go bad (high resistance to ground) so it changes the ground connection characteristics.

Also, dumb question--how's the speaker? I had a RCA console radio I had to adjust the spider on the speaker due to "tinny" sound. It's voice coil didn't appear rubbing, but was not allowing the cone the free flowing action it needed for fidelity.
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Re: Howard 418

Post by Motorola man on Tue Mar 12, 2013 9:08 pm

Ground is good. Both of the pots on volume control & bass control pot are grounded together at the same place. All three pots test good. The speaker is fine too.
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Re: Howard 418

Post by Motorola man on Tue Mar 12, 2013 10:02 pm

I tested it after replacing the electrolytics and several times throughout the rest of the process. There was no bass from start to finish (other than the 60 Hz hum at the beginning).
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Re: Howard 418

Post by Bill Cahill on Tue Mar 12, 2013 11:21 pm

Have you checked voltages on the bass boost tube? Have you tried subbing that tube? Maybe the socket is dirty, and, pins not making contact??
Is that choke providing voltage to the plate of the bass boost o.k.?
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Re: Howard 418

Post by Ken g on Wed Mar 13, 2013 8:45 pm

I am glad that you did those steps . I wonder if someone modified it to suit someone back then . hmmm ??

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Re: Howard 418

Post by Motorola man on Fri Mar 15, 2013 10:55 pm

I took a brief look at it again today and found that the choke is open. Hopefully it will be an easy fix... fingers crossed.
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