- rockola amp 52280-a hums - 2 Updates
- Fender Frontman 212R Volume 80% down problem - 6 Updates
- Welder Power - 8 Updates
| daves <f6ceedb9c75b52f7fcc0a55cf0cfbf5d_1026@example.com>: Nov 26 04:37AM I bought a used amp for my 488 rockola. the old amp worked but one channel fuzzy and lower volume than the other side. The used amp hums but works. disconnecting the pickup doesn't change. Maybe the 2 large silver capacitors? -- |
| N_Cook <diverse@tcp.co.uk>: Nov 26 08:12AM On 26/11/2015 04:37, daves wrote: > fuzzy and lower volume than the other side. The used amp hums but > works. disconnecting the pickup doesn't change. Maybe the 2 large > silver capacitors? What does AC volts range on a DVM show for the main caps? |
| dansabrservices@yahoo.com: Nov 25 09:24AM -0800 If there are ultrasonic frequencies being amplified, you wont hear them. But... they will cause the amp to work really hard and generate more heat than usual. This could cause the amp to shutdown due to the heat. Other than using a scope, there is no way to confirm this. Dan |
| Leonardo Capossio <capossio.leonardo@gmail.com>: Nov 25 09:48AM -0800 El miércoles, 25 de noviembre de 2015, 13:13:52 (UTC-3), Leonardo Capossio escribió: > Don't have a scope, best I can do is a DMM. > Just to clariphy, the audio from the amp gets cut abruptly. Everything is working like a charm, the sound isn't fading away or anything, and the suddenly it stops outputting audio. Everything else seems to be working. > In this case, the only thermally dependent element I see is the PTC100. The circuit surrounding the PT100 seems to be compensating the bias current of the power amp, though I do not understand it fully, if anyone can point to a source that explains how this circuit work it would be great. To me it seems very strange that it abruptly cuts out the sound. To clarify, the heatsink is working correctly, but I cannot measure the temperature because I don't have anything reliable to do it with. |
| Leonardo Capossio <capossio.leonardo@gmail.com>: Nov 25 09:50AM -0800 > If there are ultrasonic frequencies being amplified, you wont hear them. But... they will cause the amp to work really hard and generate more heat than usual. This could cause the amp to shutdown due to the heat. Other than using a scope, there is no way to confirm this. > Dan If there are ultrasonic frequencies (which I cannot measure), then what could cause this ? Where might they be generated ? The amp is shutting down via the PT100 circuit, that should also do some temperature drift compensation. If I bypass this compensation, would the amp sound very bad ? |
| jerryrego03@gmail.com: Nov 25 01:18PM -0800 On Wednesday, October 14, 2015 at 10:18:15 AM UTC-5, Leonardo Capossio wrote: > a power amp problem (because fortunately it has a pre-amp out and pwr > amp in) > Thanks. Did you check the 42v and -42v once the amp went into the low volume state? |
| Leonardo Capossio <capossio.leonardo@gmail.com>: Nov 25 06:18PM -0800 > > amp in) > > Thanks. > Did you check the 42v and -42v once the amp went into the low volume state? No, but I don't notice the LED brightness to be down not even a little bit, or the cooler. |
| Phil Allison <pallison49@gmail.com>: Nov 25 07:23PM -0800 Leonardo Capossio wrote: > current of the power amp, though I do not understand it fully, if > anyone can point to a source that explains how this circuit work it > would be great. ** PTC100 operates the "mute" function of the power amp by shutting off Q7 and so the base voltage to Q8 - which is a 2mA current source for the input pair Q9 & Q10. This results in no current in the driver stage - transistors Q11, Q12 & Q13 and so no amplification. .... Phil |
| OldGuy <nospam@spamnot.com>: Nov 25 11:41AM -0800 Welder is rated 240VAC 60Hz 20A single phase. How to connect to house 220VAC 60Hz that is two phase 120VAC? House is 20A. 220VAC coming from unused dryer connector. --- news://freenews.netfront.net/ - complaints: news@netfront.net --- |
| Jon Elson <jmelson@wustl.edu>: Nov 25 01:59PM -0600 OldGuy wrote: > House is 20A. > 220VAC coming from unused dryer connector. > --- news://freenews.netfront.net/ - complaints: news@netfront.net --- Connect the welder to the two "hot" wires and safety ground. It is 220 (or more likely 240-250 V) between the two hot wires of the dryer outlet. Jon |
| Tim Wescott <seemywebsite@myfooter.really>: Nov 25 02:01PM -0600 On Wed, 25 Nov 2015 11:41:47 -0800, OldGuy wrote: > How to connect to house 220VAC 60Hz that is two phase 120VAC? > House is 20A. > 220VAC coming from unused dryer connector. It's not really two "phase" -- it'll be the typical North American two legs and ground system, where each leg is 120V off of ground, and the two legs (both of which go to the dryer outlet) are 240V from each other. You say "house is 20A" -- do you mean there's at least a 20A circuit to the dryer? If so -- plug it in and have fun. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
| "Ralph Mowery" <rmowery28146@earthlink.net>: Nov 25 03:18PM -0500 "OldGuy" <nospam@spamnot.com> wrote in message news:n35304$2cfa$1@adenine.netfront.net... > How to connect to house 220VAC 60Hz that is two phase 120VAC? > House is 20A. > 220VAC coming from unused dryer connector. I hope that damn 2 phase 220 house wire does not start up again. There is a true 2 phase and then then there is the split phase 240 that is common in most of the houses in the US that some try to claim is 2 phase. If the power is comming from a standard 240 volt dryer connector, there will be 3 wires. Two of them are hot and the third is a combination of neutral and ground. If the welder has only 2 wires and a ground, then hook up the two hot wires of the welder to the two hot wires at the outlet. Then connect the ground/chasses of the welder to the ground/neutral wire of the outlet. |
| "pfjw@aol.com" <pfjw@aol.com>: Nov 25 12:48PM -0800 On Wednesday, November 25, 2015 at 3:12:24 PM UTC-5, Ralph Mowery wrote: > I hope that damn 2 phase 220 house wire does not start up again. There is a > true 2 phase and then then there is the split phase 240 that is common in > most of the houses in the US that some try to claim is 2 phase. OK - I live near Philadelphia - which, together with Baltimore, MD shares one of the last areas in the US where one may still get actual 2-phase power. 2-phase, 4-wire power was developed primarily for heavy motor use in that era when the battle of AC vs. DC was not yet settled and 3-phase power was barely a gleam in Tesla's Eye. (SIDE NOTE: The last DC building in NYC fed from the Pearl Street Station (for ~125 years) went down in 2007.) For whatever reason, both Philadelphia and Baltimore accumulated an inventory of heavy freight elevators that use 2-phase motors to this day, such that the local utilities continue to supply the power to a very few customers in specific locations within each city. I had the privilege of working on several such elevators and heavy water pumps in my youth while working my way through school as an electrician. NOTE ALSO: some few households at the time also got 2-phase. And both PA and Reading railroad workers living along the rights-of-way got 25-Hz current - used for railroad traction motors, also to this day. Standard household power in the US is 1/3 of a Delta-connected 3-phase system, being hot-to-Hot at a nominal 240V and hot-to ground at 120V. Single-phase as only 1/3 of the total capacity is realized. All this is done in the single-phase transformer at the sub-station, not the distribution transformer at the pole (vault) in the neighborhood. Peter Wieck Melrose Park, PA |
| "Tom Miller" <tmiller11147@verizon.net>: Nov 25 04:00PM -0500 "OldGuy" <nospam@spamnot.com> wrote in message news:n35304$2cfa$1@adenine.netfront.net... > House is 20A. > 220VAC coming from unused dryer connector. > --- news://freenews.netfront.net/ - complaints: news@netfront.net --- Your house dryer connection is still single phase but has a neutral if it has four terminals. It will have a L1, a L2, a Neutral, and a Ground terminal. You will want to connect the welder to the L1 and L2 terminals (240 volts) and the Ground. Three wires total. Dryers usually use a 30 amp connector so you will want to find the correct connector and use 30 amp wiring into the welder. Some older dryer connections were just three wire and used the ground as the center tap (for the 120 volt parts of the dryer). That is the best I can tell you without seeing everything. |
| "Ralph Mowery" <rmowery28146@earthlink.net>: Nov 25 04:26PM -0500 <pfjw@aol.com> wrote in message news:c88c56ad-89a5-47b0-a599-4ee4dc142dcd@googlegroups.com... On Wednesday, November 25, 2015 at 3:12:24 PM UTC-5, Ralph Mowery wrote: >>distribution transformer at >>the pole (vault) in the neighborhood. >>Peter Wieck >>Melrose Park, PA I know that in some parts of the country you may run into many different kinds of power in the houses, just not too common. Only reason I mentioned the 2 phase stuff was because of the origional question. I doubt that a house hold dryer would be 2 phase, but who knows ? I bet it would be difficult for the average home owner to have a house wired with anything but the standard 120/240 system of most of the country and get anything to work. Living in the south I doubt much if any of that 'odd ball' power was used. About the only "odd" voltage I see is some 208 volts phase to phase with 120 to the neutral instead of the 240 p to p. |
| Bill Martin <wwm@wwmartin.net>: Nov 25 04:01PM -0800 On 11/25/2015 11:41 AM, OldGuy wrote: > House is 20A. > 220VAC coming from unused dryer connector. > --- news://freenews.netfront.net/ - complaints: news@netfront.net --- Might want to take a look at the wires going to that dryer connection...there was a period some years ago when Aluminum wire was in vogue for such things as dryers and kitchen stoves. 1960's time frame if I recall right. That's not really a good thing for a welder...and lots of other loads. |
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