Search results

Heading out on the 29th for a two week ride up thru New England. Have had to content myself with local rides for the last 2 years- finalizing the motels now. Bike & luggage is sorted and ready... :)

Seems plausible. I like testing amps with square waves to observe ringing and power supply stiffness, and frequency excursions to observe the rolloff and how the slew rate holds up, and how the amp performance degrades. If my 3150 goes onto the bench again for some reason it would be...

I didn't do detailed power tests on the 3150, but given its performance otherwise I would expect it to generally meet the 50watt spec in terms of power supply and power amp throughput Less sure of how it would do given square waves or frequency extremes into 4 ohms. I found the unit to run...

Did some more work on this unit, finally :) I removed the fixed bias resistors, since the measured bias voltages were quite a bit different- the manual suggests putting a 68ohm in parallel with a 200ohm pot- I ended up just putting in 15 turn pots (500 ohms I had on hand). A 25mv or so...

In the garage; Cornershop- Nikko 6065 thru 4 JBL 2600's. I was wondering why the unit's been sounding so funky. So I took the grille cloth off the oddball speaker; woofer paper cone torn all the way around lol... I have a couple spare woofers in the stash, so swapped in a new one -...

I have it broken down but its on hold for a bit- I happened upon an old tube receiver that I've been overhauling; so at least its not a newer project lol. That said Its not a bad system- I have a newer regular fisher with integrated amps- this one is a more modest design yet better built in...

C543, C544 are part of the op-amp tone control circuit, C601-604 are coupling caps into the front end of the power amp. I'd put pretty much any electrolytic in there, 16v or higher rating is fine- its all low voltage audio. If you wanted to be fancy, then you might choose tighter tolerance...

100v there in place of 63v is no problem... its part of the amp bridging circuit, so there are rail voltages nearby- just don't want to go lower voltage.

I think so... I mounted the triac via an existing screw thru an otherwise unoccupied corner of the rectifier board of the 100 watt Kenwood, so no good heat conduction. I put a heatsink on the triac- never got warm.

Make sure the to-220 tab is electrically isolated (assuming the part you're using has an exposed tab). That means a mica/silpad and and isolation bushing for the screw (so it cannot touch any part of the tab, but still clamp it down).

Followup for posterity; Here is the current schematic. I'm finding .1 uf coupling caps instead of .047, and 4 to 5k plate resistors instead of 10k gives the unit a bit more headroom. And, when running wires thru the chassis base, be sure the grommet material is non-conductive. I was...

My buddy came over with his meter, we measured 29ma plate current on one of the 45's with 1kc in and levels peaked- so it looks as if I'm getting my money's worth out of the power amp. Definitely not getting it out of my meter however, might be time for a new one.

Ah, thats the "Quality Condenser".. removing that brought up the top end well.The 50's vintage Stromberg/Carlson speakers I'm using have very bright tweeters which makes them a fairly good match for the amp's power curve. I probed earlier in the circuit, looks like most of the rolloff is...

Just as a followup, I did a power measurement of the amp, got about 5.5watts peak with a 1kc sine input- input and volume knob peaked. I swept the audio band at max power, the amp held up down to 30hz or so, the amp starts to roll off at 4kc and above regardless of output power.

I am getting a 5watt sort of vibe out if it.. .maybe I'm chasing power that isn't there lol- will keep that in mind. THanks!

I don't see signs of the pentode kink which looks to me like it comes from a too-low plate voltage, my noisy low level is solved by flipping the input coupling xformer, but that cuts down the max gain of the 24's which then needs a larger plate resistor to swing into the 27's input circuit. My...

Sure do.. mine is a late model 55C but had a few early model tube resistor values. Digging through all the variations of parts was interesting to say the least. The resistors formed by wire wrapped around bakelite/phenolic cores are also a pest. One of mine was blown out the others were...

I have my Atwater Kent 55C working now, the transformer potting tar was annoying and the wax capacitors were nasty, but aside from that its proving to be an easy unit to work on and debug. I don't care about AM reception so modified the set to take a modern line level aux input, through the...

I've had somewhat better luck with vintage tuners than modern digital- at least on marginal signals. Some of it might be the marginal signal can "sit there" instead of being in and out of lock.. there is one station worth listening to around here and reception isn't great so I really...

Its been a while since I took up a new system repair project. For some time I was on a high-power kick- which is fun, but I wanted to change things up. So I found this old weird Fisher quad on ebay- definitely a low end system from the day but no unobtanium parts- the amp is NPN...

I'm not a big fan of faired Goldwings but love them when set up "naked" like this- I bet that thing really scoots too :)

But with the transformer primary in series can that instantaneous peak current occur? I was thinking low-ish gate resistance of the triac was dividing down the trigger voltage, so delaying turn-on and putting a big spike into the primary.

Not part of the religion, but I recently ran out of my usual Edge foam and resorted to a badger brush and cream which my father gave me for Christmas a while back. He's part of the shaving cult and was trying to suck me in. I decided I like the brush and cream thing for 2 reasons; 1. The...

A triac with isolated tab is fine if you can find one but arranging isolation is trivial- you'll already be ordering the semiconductor, adding a mica/silpad, isolating collar and cheapie heatsink is only a few $ more. 1/2 watt or more is fine for the resistor its not critical once you have a...

Note the location of the triac, mounted on a heatsink- a tab isolator and silpad or mica is needed- grounding the tab to the chassis will short and probably destroy things. The location for the triac is advantageous, its easy to reroute the 120v leads back to it. After I took this pic I...