A real Hummer

[gator7]

A buddy of mine just got a Mk IV off ebay. First problem, he paid a lot. Second The radio came w/ a cracked 6BA6 I think. Now for the real Issue. It has a nice hum you can hear in the speaker. He tells me that the hum can also be heard in the modulation. I have not heard it on the air. But I heard the hum up close. you can hear it from 5 feet away from the speaker. The volume set at 1/4. It's bad.
Is the power supply bad. Or do we have a bad filter cap? Or am I way off?
Any ideas??

[Tombstone (R.I.P.)]

Like Mark 4 said, bad filter capacitors in the power supply. I would replace them in both the transmitter and receiver but the radio still should have the 100,000 mile tune up.

Tombstone

[gator7]

A buddy of mine just got a Mk IV off ebay. First problem, he paid a lot. Second The radio came w/ a cracked 6BA6 I think. Now for the real Issue. It has a nice hum you can hear in the speaker. He tells me that the hum can also be heard in the modulation. I have not heard it on the air. But I heard the hum up close. you can hear it from 5 feet away from the speaker. The volume set at 1/4. It's bad.
Is the power supply bad. Or do we have a bad filter cap? Or am I way off?
Any ideas??

That was what I was thinking also. I'll pass it along. Thanks.


73's

[2600]

So, if I have a 30 year-old car, and ALL the hoses under the hood are original, can I fix it by just replacing the one that leaks today?

Think of your "hum" as if it were caused a dry-rotted, stiff 30 year-old rubber hose. In this case, replacing all of the electrolytic capacitors is a lot like replacing every original hose, whether it leaks today or not. You know that if you just "patch" the one that's bad, you'll surely see another one fail before you drive it very far.

If you have the equipment to test individual electrolytic capacitors, you might get by with just replacing the filter caps that check bad TODAY.

But the only way to fix it so it will run for any length of time is to replace every electrolytic cap in the receiver and the transmitter, too.

But that's only if you want to keep the thing and use it regularly.

If you plan to sell it, that would be a reason to just "patch" what's broke today, and leave the other original filter caps where they are, so long as they still work.

But then you would need a way to test them.

Much simpler to just replace them all. And it's the only way to put the radio back into regular, reliable service.

There are some kinds of tube failure that can create a hum in the receiver or the transmitter. But the odds favor one or more bad electrolytic caps as the root of this problem.

73

[mark4]

That is why I always recommend ALL the old electrolytic capacitors get changed. Some brainiac on the net wanted to argue with me about this point. He claims you don't need to change out those old caps. The radio usually only needs the chassis dusted and blown out. GOOD LUCK WITH THAT!
Self proclaimed experts like that don't even work on these radios.
And are clueless.

[Deleted]

Based on reccomdations of several people here, Sandbagger, Nomad, MarkIV, Fixr, etc, I replace all the electrolytics in any radio that is about 25 years old or older. This means any radio with tubes, and many classic solid state radios from the late 1970's and early 1980's.

I have even upped the voltage on some caps of the solid state units. Since the caps have become smaller for the same values, I typically don't go under 25V. If they are a higher voltage after 25V, I just match the same voltage. One reason I do that is many of the radio's I have worked on have had their power supply voltage turned up to unreasonably high levels, like 17.5 volts, instead of 13.8 volts.

Mouser has great prices on caps, and if you can do the work yourself, you save a ton of money. Their shipping is usually like $8 for the first pound, so don't order just 1 or 2 caps. The same caps (Xicon or Nichicon) at Radio Shack that cost $1-2, cost pennies at mouser.

[gator7]

I have learned that on this forum. Its pay me now. Or pay me latter. Like the commercial said.
I am glad to say that this is not my Mk IV. The guy that purchased it may do just what 2600 suggested. Patch it up and send it on it's way.
Now that I have a bit more knowledge about old tube classic radios. I must say that the guy who had a (I think) MK III (CRS) on ebay who had Barkett go though it. Well he didn't get his reserve. The bidding ended at 700.00 and some change. He had the right idea. But not the right time.
Without a doubt the repaired eagle would be the best buy, The repair bill was $561.00 and some change. That's great for the buyer. But it makes it hard for the seller to re-capture his investment.
It is hard to justify paying over 700.00 for a 30-35 year old classic that sold for 750.00 when NEW. I am quoting GRUMPY here. At first I didn't agree with him. But when you look at it from a common since standpoint. Its true. Why pay more than it cost to begin with?
I guess that means i won't own that Classic 55 Chevy that I always wanted..

Oh well.

Maybe when the Price come down

[Deleted]

I won't buy classics on ebay, unless they are listed for repair. The price is significantly reduced.

Couple things about ebay:

1. If you buy from the "I don't know anything about these radios, and being sold as-is", then you are a d**n fool. It translates to, it doesn't work. Most often, people will try and see if the product works. That is why untested is a bogus term. Secondly, if you buy a radio which only has been turned on and the lights come up, you are a d**n fool. That just means that they power supply works. (Unless you are paying at significantly reduced prices).

2. If you are buying from a person that is not familiar with CBs, you are asking for trouble.

3. Feedback. If you do not use this great tool, you are a d**n fool. I have seen many people complain about the item, and I look at the sellers feedback, and he had problems in the past.

4. Questions. Ask the seller, what the condition is on a scale of 1-10, condition of the face, does it smell like smoke, etc. If he does not answer all or any of your questions, then you are looking for trouble. I cannot tell you how many times I have asked these questions, and do not get a response.

5. Pictures. Do not go by the ebay pictures. They are poor. If the seller is not using Photobucket, Imageshack, or other picture server, then ask for close-ups thru email. I have had good luck with this as some have sent me better pictures. The ones who give me no response or a runaround, I avoid.

6. Condition misinterpretation:

Mint - Should be new in box condition. It it was even used in the slightest, it is not mint. Must be stock and un-modded.

Near mint - Should be what "mint" is supposed to be. It should appear nearly flawless, with no imperfections that you can pick out immediately. If you have find some after, looking really hard, then that is OK. Should be perfectly clean. I sometime use "excellent" for this.

Very Good - Used with some noticeable wear or scratches, but nothing that is really that bad. Should be clean.

Good - Had several scratches and wear marks easily visible, but is in solid shape. Should be clean. Good should really be "used but clean" condition.

Fair - In one piece, but dirty, numerous scratches, wear marks, etc.

Poor - Missing pieces/parts, not complete, dirty.

That is just what I use as others might have differing opinions. But I cannot begin to tell you how many near mint things I see on ebay, especially with unit that have switches and mods that are visible.

FYI, the TRC-455 that I restored, I bought on ebay for $12+$15 shipping. Had no pictures, and was listed as a repair. I asked the seller and he said it needed cleaning, and was dirty, and told me the problem. He was dead on as it looked as I expected. But I got it for $27. But after the cleaning, I could not believe what I had on my hands. I had it in pieces and cleaned every inch. And I mean pieces.

[Deleted]

Also, the only mint or near mint thing I will buy, has to be face to face. I want to see the thing. I am interested in a GE superbase, and a local has one. I am going to take a look at it. He says it is mint.

I have seen GE Superbases on ebay, listed as pristine, mint, virgin, etc. The virgin one has a switch installed on the back. I questioned the seller, and he did not repsond. He also did not post the question on the ad, which means he did not want anyone to see. I instead listed the info here.

Maybe we should have an "ebay evalutation" section on this forum, so we can spot bad auctions, and list the link for informational purposes. Night Ranger has a good one on the amplifier he found.

[Sandbagger]

Jan 11, 2009 10:55:16 GMT -5 @vinnies said:

I won't buy classics on ebay, unless they are listed for repair. The price is significantly reduced.

Couple things about ebay:

1. If you buy from the "I don't know anything about these radios, and being sold as-is", then you are a d**n fool. It translates to, it doesn't work. Most often, people will try and see if the product works. That is why untested is a bogus term. Secondly, if you buy a radio which only has been turned on and the lights come up, you are a d**n fool. That just means that they power supply works. (Unless you are paying at significantly reduced prices).

2. If you are buying from a person that is not familiar with CBs, you are asking for trouble.

3. Feedback. If you do not use this great tool, you are a d**n fool. I have seen many people complain about the item, and I look at the sellers feedback, and he had problems in the past.

4. Questions. Ask the seller, what the condition is on a scale of 1-10, condition of the face, does it smell like smoke, etc. If he does not answer all or any of your questions, then you are looking for trouble. I cannot tell you how many times I have asked these questions, and do not get a response.

5. Pictures. Do not go by the ebay pictures. They are poor. If the seller is not using Photobucket, Imageshack, or other picture server, then ask for close-ups thru email. I have had good luck with this as some have sent me better pictures. The ones who give me no response or a runaround, I avoid.

6. Condition misinterpretation:

Mint - Should be new in box condition. It it was even used in the slightest, it is not mint. Must be stock and un-modded.

Near mint - Should be what "mint" is supposed to be. It should appear nearly flawless, with no imperfections that you can pick out immediately. If you have find some after, looking really hard, then that is OK. Should be perfectly clean. I sometime use "excellent" for this.

Very Good - Used with some noticeable wear or scratches, but nothing that is really that bad. Should be clean.

Good - Had several scratches and wear marks easily visible, but is in solid shape. Should be clean. Good should really be "used but clean" condition.

Fair - In one piece, but dirty, numerous scratches, wear marks, etc.

Poor - Missing pieces/parts, not complete, dirty.

That is just what I use as others might have differing opinions. But I cannot begin to tell you how many near mint things I see on ebay, especially with unit that have switches and mods that are visible.

FYI, the TRC-455 that I restored, I bought on ebay for $12+$15 shipping. Had no pictures, and was listed as a repair. I asked the seller and he said it needed cleaning, and was dirty, and told me the problem. He was dead on as it looked as I expected. But I got it for $27. But after the cleaning, I could not believe what I had on my hands. I had it in pieces and cleaned every inch. And I mean pieces.

All good stuff and I'd add that in those cases of "I don't know anything about radios" or "I plugged it in and it lights up" that should suggest to the seller that any price that he thought he might get will be severely reduced. So I look for those along with a good price. I am more than willing to take a chance on a cosmetically good, but electrically questionable radio. There are very few electrical things which can't be fixed or replaced in some way. There are some radios where the parts are no longer available, but they're usually newer radios with IC's.

And as for pictures, many times the pictures shown are NOT of the exact radio being sold, but just one of that model. I've caught people lifting pictures of radios from my website (along with my review as their selling description). In some cases the seller might not have a digital camera, and this is better than no picture. But other times unscrupulous sellers are trying to scam you. So it's buyer beware. Sometimes what you see isn't what you'll get, especially if you're more concerned about cosmetic condition.

[Sandbagger]

Jan 11, 2009 9:41:19 GMT -5 @vinnies said:

Based on reccomdations of several people here, Sandbagger, Nomad, MarkIV, Fixr, etc, I replace all the electrolytics in any radio that is about 25 years old or older. This means any radio with tubes, and many classic solid state radios from the late 1970's and early 1980's.

I have even upped the voltage on some caps of the solid state units. Since the caps have become smaller for the same values, I typically don't go under 25V. If they are a higher voltage after 25V, I just match the same voltage. One reason I do that is many of the radio's I have worked on have had their power supply voltage turned up to unreasonably high levels, like 17.5 volts, instead of 13.8 volts.

Mouser has great prices on caps, and if you can do the work yourself, you save a ton of money. Their shipping is usually like $8 for the first pound, so don't order just 1 or 2 caps. The same caps (Xicon or Nichicon) at Radio Shack that cost $1-2, cost pennies at mouser.

I usually try to replace all electrolytics in the tube rigs, but I won't on solid state unless there are specific cap-related issues. There are way more small electrolytics in a modern SSB rig, and it becomes labor intensive to shotgun all of them. Usually the most common electrolytics to fail are those darned 10V'ers. I just fixed up a SuperStar 360 (That I originally bought new in 1984) for a friend of mine that had no receive audio. The problem turned out to be one of the 10V caps shorted on the B+ line to the squelch switch. Since I had a bunch of those 2.2 uF's I replaced all the 10V'ers in that radio. But that was still only a fraction of the total number of electrolytics in that radio.

[2600]

The "Ten-Volt Blues", eh?

73

[Sandbagger]

Jan 11, 2009 23:35:37 GMT -5 2600 said:

The "Ten-Volt Blues", eh?

73

You know it......

I see it so often, that I have to wonder why the 10V caps seem to have such a high incidence of failure compared to equally old, but higher value caps. Is there something inherent in the design of the low voltage caps that makes them more likely to short?

I wouldn't think a 10V cap on an 8V supply line would be any worse than a 16V cap on a 13V line.......

[Tombstone (R.I.P.)]

I wasn't suggesting to replace just the power supply filter caps unless it's a patch job to make the radio run for resale. I agree that all caps must be replaced in a rig that you're going to keep and use. That guy who thinks that you don't need to replace old capacitors is way off base. One question though. Will old disk capacitors cause crackling, static, and such and should they be replaced along with all of the electrolytics? Yeah, I also agree with using caution when buying radios on Ebay. Those discriptions usually mean that the radio has flaws. I once saw a radio listed that was "mint" Do the make radios in mints? I thought that only money was made in them. This mint radio was described as in perfect working order because all of the lights came on with a hum in the speaker and when keyed up the transmit light came on. Only trouble was that they had no antenna to connect to it so they couldn't talk to anyone!

Tombstone

[gator7]

I understand the buy it for repair idea. And I agree it is a good way to buy them cheap. But If you have limited knowledge of repair capability. Then you either will need to find a Browning/Tram tech. Or ask a lot of questions here. And hope that you can get buy with your limited knowledge. So that makes the Lights up, great condition appealing to some of us.
It's a catch 22.
Or. If you have deep pockets. Problem solved. ;D

73's and thaks to all who have given your input.