Welcome Guest! Be sure you know and follow the Phorum Rules before posting. Thank you and Enjoy! (January 12) x

Thread Closed
Thread Rating:
  • 1 Vote(s) - 5 Average
  • 1
  • 2
  • 3
  • 4
  • 5

model 20 hum (detector circuit?)
#60

(11-08-2015, 10:28 PM)Ron Ramirez Wrote:  The voltages were originally measured at the factory with meters with a sensitivity of 1000 ohms per volt. That's all they had at the time. Those meters loaded the circuit under test, resulting in voltage readings that were actually incorrect!

Today, we can easily buy digital multimeters with input impedances in the megohms per volt, which do not load down the circuit under test as did the old meters from ye olden days.

You can acquire an old early 1930s voltmeter...or find a low-end analog multimeter made by Calrad and sold in the 1970s...or maybe someone will measure the voltages in their working model 20 and share the results here. I no longer own any Model 20 sets.

I have never taken the voltage reading very seriously in any radio I repaired, except for transistors and tube bias. Otherwise most problems are fairly obvious. It looks like I have found my problem. While I live in a building built new, four years ago everything should be fine electrically. I have two other radios, both transistor, from the early 70's and they work just fine. However today I took the radio to a friend who repairs radios for a living, in Santa Clarita and the hum wasn't objectionable at all. The radio worked as it should. His suggestion to me was to get an isolation transformer and said that might not even be enough, it might be the area I am living in. So thanks to everyone for all your suggestions.


Messages In This Thread
model 20 hum (detector circuit?) - by Tubesforme - 10-19-2015, 01:11 PM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-19-2015, 06:23 PM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-20-2015, 10:01 AM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-25-2015, 10:57 AM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-25-2015, 11:39 AM
RE: model 20 hum (detector circuit?) - by morzh - 10-25-2015, 11:08 PM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-26-2015, 10:18 AM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-26-2015, 10:34 AM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-26-2015, 11:24 AM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-27-2015, 08:43 PM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-28-2015, 11:52 AM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-28-2015, 03:36 PM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-30-2015, 06:13 PM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-31-2015, 10:40 AM
RE: model 20 hum (detector circuit?) - by Tubesforme - 11-09-2015, 08:11 PM
RE: Low continual hum in model 21 - by Tubesforme - 10-23-2015, 11:19 PM



Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
Testing a speaker and output transformer Trutone A2-G
You guy's are right on. I found a broken wire on the speaker plug that I replaced and all is well now. Have better volu...murf — 03:43 PM
Philco model 38 code 121 not receiving signal.
I need to get a vtvm. I think that little component tester is just more accurate. Plus it shows the inductance which is ...Stormlord5500 — 03:07 PM
Philco model 38 code 121 not receiving signal.
I use a pair of Mastercraft brand DMMs from Canadian Tire, from what I read most of those DMMs use the same main chip re...Arran — 02:36 PM
Philco model 38 code 121 not receiving signal.
Thank you sir. Yes I feel good and also relieved because this one's been weighing on me a bit.Stormlord5500 — 11:18 AM
Philco model 38 code 121 not receiving signal.
It feels good don't it? Good luck on the rest.Paul Philco322 — 11:06 AM
Philco model 38 code 121 not receiving signal.
I've reinstalled the coil. Now IT'S ALIVE!!!!!! I fired up my TinySA on signal generator mode and set it to 1400Kc and ...Stormlord5500 — 11:01 AM
Philco model 38 code 121 not receiving signal.
Yes, Walmart, right up there with Fluke.RodB — 11:00 AM
PT 6 chassis screws size???
it certainly won't be metric! SAE threads were all that was known then. Take care, - GaryGarySP — 10:58 AM
Philco model 38 code 121 not receiving signal.
I think this thing is way more accurate than my Walmart DMM. :DStormlord5500 — 08:19 AM
Philco model 38 code 121 not receiving signal.
Thankyou for the kind words sir. I double checked it with my component tester and it read 2.7 ohms at .02mH.Stormlord5500 — 08:14 AM

[-]
Who's Online
There are currently 2011 online users. [Complete List]
» 1 Member(s) | 2010 Guest(s)
Avatar

>